Hybridization of MOFs and polymers

From waste to wealth: Glycolysis of PET for high-value resource utilization

The extensive application of plastic products has led to the accumulation of substantial quantities of polyethylene terephthalate (PET) waste. How to recycle the increasing PET waste is becoming a global challenge. The chemical recycling of PET, which employs a depolymerization-repolymerization approach to maximize resource value, has garnered growing attention from the scientific community. Of the numerous PET recycling methods proposed, glycolysis is especially promising because of its mild reaction conditions and the ease of separating the products. This paper explores the progress and obstacles in the glycolytic transformation of PET into bis(2-hydroxyethyl) terephthalate (BHET), covering aspects such as the glycolysis mechanism, process flow, catalyst development, optimization of reaction strategies, and reaction kinetics. Notably, the primary challenges in PET glycolysis are slow reaction rates and poor product selectivity. Various effective strategies have been proposed to address these issues, and their advantages and disadvantages are discussed. Furthermore, the potential applications of the BHET monomers are explored. Finally, the challenges and future prospects of glycolysis are presented. This review aims to offer valuable insights into glycolysis and act as a helpful reference for developing high-performance catalysts and advancing industrial applications.

Evaluation of metal-organic framework/layered double hydroxide-embedded sodium alginate beads for effective removal of tartrazine dye: A comparative analysis of RSM and ANN

NiFe-layered double hydroxide supported metal-organic framework-embedded alginate bead composite (MIL-88 A/NiFe-LDH@SA) was developed and investigated for the removal of tartrazine food dye (TTZ). Structural characterizations of MIL-88 A/NiFe-LDH@SA were determined by the measurement of FTIR, XRD, BET, SEM, and EDX. Response surface methodology (RSM) and artificial neural network (ANN) were applied to predict the removal of TTZ dye. The optimization of the relevant parameters was obtained via the central composite design (CCD) in RSM. The numerical optimization revealed that a maximum removal efficiency of 94.82 % was achieved at Co of 8.02 mg/L, pH of 3.74, adsorption duration of 4.72 h, and adsorbent amount of 1.33 mg/mL. A comparative analysis was also performed for RSM and ANN models. The findings show that both models can accurately predict TTZ removal efficiency. However, based on the statistical analysis results, ANN demonstrated a higher level of accuracy than RSM in predicting TTZ removal. The kinetic studies also revealed that the adsorption well obey the pseudo-second order (PSO). The isotherm studies indicated that the Langmuir-Freundlich (L-F) model was proper for explaining the adsorption behavior of TTZ on MIL-88 A/NiFe-LDH@SA. Thermodynamic studies conducted that the adsorption process is spontaneous and exothermic.

Challenges and outlooks for the polyoxometalates, metal-organic frameworks (POMs-MOFs) hybrid materials in water treatment technologies

The importance of water for life is undeniable. However, modern industrial and urban practices have led to the pollution of water reservoirs. Efficient wastewater purification is crucial for sustainability, and several materials with specific characteristics have been investigated to improve water quality. The integration of polyoxometalates (POMs) into metal-organic frameworks (MOFs) holds significant potential for water treatment applications due to their complementary properties. POMs are renowned for their high catalytic activity, redox versatility, and resistance to harsh environments, while MOFs offer high porosity, tunable chemical environments, and enhanced stability. When immobilized within MOF structures, POMs can exhibit improved processability and recyclability, overcoming limitations such as leaching and aggregation. The resulting composites maintain the catalytic efficiency of POMs and leverage the structural and adsorptive characteristics of MOFs to target contaminants in water. These hybrid systems are up-and-coming with improved characteristics where the synergy between the POM's catalytic sites and the MOF's porous network can facilitate efficient degradation of organic pollutants, heavy metal sequestration, and enhanced adsorption of micropollutants, paving the way for sustainable water purification technologies. This review encapsulates the latest advancements in POM-MOF composites, discussing the predominant synthesis strategies and their applications, particularly in wastewater treatment. Furthermore, POM-MOF composite nanoplatforms for wastewater treatment are explored based on their high stability and large specific surface area, making them an ideal choice for waste-water treatment.

Synergistic Dual-Polar-Functionalized Metal-Organic Framework-Modified Separator for Stable and High-Performance Sodium Metal Batteries

Sodium metal, regarded as an ideal anode material for high-energy-density rechargeable sodium metal batteries (SMBs), faces critical challenges, such as sluggish Na+ transport kinetics and uncontrolled dendritic growth, which severely hinder its cycling stability and practical applications. Herein, the well-designed, multifunctional separator, UFS2@GF, constructed using metal-organic frameworks functionalized with fluorinated (-F) and sulfonic acid (-SO3H) groups, synergistically provides more nucleation sites for Na+ deposition, thereby reducing the nucleation overpotential and achieving uniform deposition. The inorganic-rich solid electrolyte interphase induced by UFS2 facilitates a uniform Na+ flux and enhances charge transfer efficiency. Structural characterization and density functional theory calculations further demonstrate that the introduction of abundant sodiophilic sites provided by -F and -SO3H significantly enhances Na+ transport kinetics by reducing the energy barriers for Na+ migration within the UFS2 framework, leading to a higher Na+ transference number, superior ionic conductivity, and accelerated ion transport. Because of these synergistic effects, the symmetric cell with UFS2@GF achieves stable performance, enabling stable cycling for over 2500 h at 0.25 mA cm-2 while delivering an excellent specific capacity of 87.3 mA h g-1 at 10C in Na∥Na3V2(PO4)3 cells. These results highlight the critical role of synergistic functional group strategies in addressing the limitations of SMBs.

Pyridine-N-Anchored Ag Strategy Facilitated Br- Adsorption via Ultrahigh Exposure and Coordination Unsaturation of Ag

Traditional adsorbents using silver nanoparticles demonstrated exceptional adsorption capacities for Br-. However, the majority of the adsorption sites in silver nanoparticles are situated on their surfaces, limiting the interaction of internal atoms with Br-. Therefore, we synthesized Ag/UiO-bpy MOF by utilizing the two pyridine nitrogen atoms in the ligand to anchor silver. So each silver atom was effectively exposed. Besides, owing to the coordinatively unsaturated state of the silver atoms, they exhibited a stronger adsorption affinity for Br-. As a result, Ag/UiO-bpy demonstrated an exceptional Br- adsorption capacity of 362.6 mg/g. Notably, the adsorption capacity with respect to silver was 2083.9 mg/gAg, which surpasses all previously reported values in the literature. Furthermore, Ag/UiO-bpy exhibited rapid kinetics and exceptional selectivity in Br- adsorption experiments. This work not only fabricated a Br- adsorbent with a high adsorption capacity but also proposed a new and innovative strategy for the subsequent preparation of Br- adsorbents.

Free-standing bimetallic Co/Ni-MOF foams toward enhanced methane dry reforming under non-thermal plasma catalysis

Understanding of the structure and interfacial merits that reactive metal-organic frameworks (MOFs) undergo is critical for constructing efficient catalysts for non-thermal plasma-assisted conversion of greenhouse gases. Herein, we proposed a free-standing bimetallic (Co/Ni) MOFs supported on bacterial cellulose (BC) foams (Co/Ni-MOF@BC) toward the coaxial dielectric barrier discharge (DBD) plasma-catalytic system, of which the Co/Ni ions coordination demonstrated an intriguing textual uplifting of the malleable BC nanofiber network with abundant pores up to micrometer-scale, which could impart a more intensive predominant filamentary microdischarge current to 180 mA with stronger plasma-catalytic interaction. Remarkably, compared to the monometallic MOF@BC foams, this bimetallic Co/Ni-MOF@BC also delivered a substantially improved alkaline absorption ability as further confirmed by the CO2- temperature-programmed desorption (TPD) result. Benefiting from its 3D superiority and synergy of Co/Ni dual-regulation, the Co/Ni-MOF@BC, therefore, displayed the highest CO2 and CH4 conversion rates to 52.31 % and 71.50 %, which was above 1.5 and 1.3 times higher than those of monometallic counterparts and Co/Ni-MOF powder. Additionally, its robust cycling performance has also been evidenced by the excellent long-time DRM performance, unchanged crystallinity, morphology, and surface chemical states. By taking both the catalyst existing form and interfacial optimization of MOFs into consideration for designing a unique DRM catalyst, we believed this free-standing 3D Co/Ni-MOF@BC foams could inspire more research outputs on the design of functional catalysts with abundant pores and alkaline absorption sites to accelerate the redox kinetics of CO2/CH4 conversion.

Free Volume Space of Polymers as a New Functional Nanospace: Synthesis of Guest Polymers

Nanospace has been used as a specific field for syntheses and assemblies of molecules, polymers, and materials. Free volume space among polymer chains is related to their properties, such as permeation of gas and small molecules. However, the void has not been used as a functional nanospace in previous works. The present work shows synthesis of guest conductive polymers in free volume space of conventional synthetic resins and rubbers as a new nanospace. Vapor of heteroaromatic monomer and oxidative agent is diffused into the soft dynamic nanospace among the polymer chains under ambient pressure at low temperature. The oxidative polymerization provides the conductive polymers, such as polypyrrole (PPy), in the free volume space of poly(methyl methacrylate) (PMMA), polypropylene (PP), silicone rubber (SR), and polyurethane rubber (PU). The ratio of the free volume decreases with the infiltration of the conductive polymers. The composites exhibit the improved mechanical and gas barrier properties. The rubbers containing PPy are used as mechanical-stress sensors with both the conductivity and flexibility. The free volume space of resins and rubbers can be used as a new dynamic nanospace for synthesis of functional polymer composites.

Enhancement of Proton Conductivity in Water and Aqua-Ammonia Vapor by Incorporating Sulfonic Acid-Functionalized Polymer into MIL-101-SO3H

The design and preparation of super proton conducting metal-organic frameworks (MOFs) are of great significance for the advancement of proton exchange membrane fuel cells (PEMFCs). An effective approach to increase the sulfonic acid density and control the hydrogen bonding networks within MOFs involves incorporating polymer chains that contain sulfonic acid groups into their pore structures. In this work, we report the in situ synthesis of a polyvinyl sulfonic acid (PVS) cross-linked polymer within the nanopores of MIL-101-SO3H, resulting in the PVS@MIL-101-SO3H composite. This composite maintains high proton conductivity in pure water vapor, achieving a peak conductivity of 2.57 × 10-2 S·cm-1 at 85 °C and 98% relative humidity (RH). Significantly, the proton conductivity markedly increases in aqua-ammonia environments, reaching 1.21 × 10-1 S·cm-1 under 1.0 M aqua-ammonia vapor at 100 °C, approximately five times higher than that observed in pure water vapor. Moreover, the composite exhibits excellent stability. Therefore, this study offers an efficacious approach to enhancing the performance of aqua-ammonia-assisted solid-state proton-conducting materials.

Constructing and characterization of cyclodextrin metal organic framework and soybean hull polysaccharide polymer composite carriers: Enhancing curcumin delivery

This study aims to create composite carriers by combining cyclodextrin metal organic frameworks (CD-MOFs) with soybean hull polysaccharide (SHP) polymers for enhanced performance. A cubic structured composite carrier was successfully synthesized, exhibiting potential for delivering functional factors. Interaction between cyclodextrin (CD) and SHP was predominantly driven by hydrogen bonding forces, as evidenced by Fourier transform infrared spectroscope (FTIR), Raman spectroscopy. Characterization methods such as Powder X-ray diffraction (XRD), Differential scanning calorimetry (DSC), and FTIR confirmed successful encapsulation of Curcumin (Cur) within γ-CD-MOF@SHP. At 35 °C, with a Cur to carrier mass ratio of 1:3, loading efficiency improved after 24 h of immersion. SHP demonstrated a protective effect on Cur, reducing release in the stomach while maximizing release in the intestine, thus enhancing Cur utilization. Additionally, γ-CD-MOF composites were shown to stabilize functional factors and regulate their release. Overall, the combination of MOFs and polymers holds promise for functional factor delivery.

A Eu-MOF-Based Fluorescent Sensing Probe for the Detection of Tryptophan and Cu2+ in Aqueous Solutions

Abnormal tryptophan (Trp) metabolism can be used as an important indicator of chronic hepatitis, paranoia, Parkinson's disease and other diseases. Deficiency or excessive accumulation of Cu2+ can cause diseases such as Wilson's disease and Alzheimer's disease. Eu-based metal-organic framework (Eu-MOF) was successfully prepared for fluorescence sensing of Trp and Cu2+ in an aqueous solution (pH = 7.4). Eu-MOF showed high selectivity and sensitivity for Trp and Cu2+ with detection limits of 0.22 µM and 0.09 µM and Ksv of 6.17 × 103 M- 1 and 2.37 × 104 M- 1 respectively. Trp and Cu2+ had overlapped UV absorption spectra with that of Eu-MOF and competed for the excitation light source. Trp also attenuated the antennae effect of organic ligands on Eu-MOF, thus quenching the red fluorescence of Eu-MOF. This study provides insights into the application of MOFs in bioanalysis and diagnostics.

Impact of Grafting Density on the Assembly and Mechanical Properties of Self-Assembled Metal-Organic Framework Monolayers

Polymer-grafted metal-organic frameworks (MOFs) can be used to form free-standing self-assembled MOF monolayers (SAMMs). Polymer chains can be introduced onto MOF surfaces through either the ligands or metal nodes using both grafting-to and grafting-from approaches. However, controlling the grafting density of polymer-grafted MOFs has not yet been achieved, because a means to control the density of grafting sites on the MOF surface has not been developed. In this study, the grafting density of polymer-grafted UiO-66 (UiO = University of Oslo) was controlled by functionalizing a portion of the Zr(IV) secondary building units (SBUs) on a UiO-66 surface with a so-called blocking agent. The remaining sites on the UiO-66 SBUs were functionalized with polymerization initiation groups, and polymers were grown from these sites to obtain particles with variable grafting densities and chain lengths that form SAMMs at an air-water interface. Even under conditions of low grafting density, these materials retain the ability to form SAMMs and their free-standing ability. Changes in particle arrangement within the monolayers were investigated using SEM imaging, and the toughness of the monolayers was evaluated using a film-on-water (FOW) method. Furthermore, coarse-grained molecular dynamics simulations were carried out to elucidate the morphology and mechanical properties of the monolayers. Findings from both experiments and simulations indicate that the toughness of SAMMs is more heavily influenced by the chain length of the grafted polymers than by the overall polymer content in the composite.

Engineering of Polyisoprene Networks Enabled by Host-Guest Thiol-Ene Reaction

Regulating cross-linking of polymers is critical for optimizing the physical properties of polymer networks. Herein, we present a strategic approach for designing polymer networks using dithiol-functionalized metal-organic frameworks (MOFs) with both one- and three-dimensional pore architectures. Upon thermal treatment, thiyl radicals were generated from the MOFs through the dissociation of S-H bonds, as confirmed by electron spin resonance measurements. Unlike in solution and bulk phases, the confinement of these radicals within the MOFs effectively suppressed homocoupling reactions, thus enabling their function as densely packed cross-linkers. The thiol-ene reaction between the MOFs and cis-1,4-polyisoprene (PI) chains, followed by the selective removal of MOF hosts, resulted in PI networks that retained the original structural features. The ordered alignment of the PI chains enhanced their thermal stability compared with the randomly cross-linked PI network.

D-Histidine modulated chiral metal-organic frameworks for discriminating 3,4-Dihydroxyphenylalanine enantiomers based on a chemiluminescence quenching mode

BACKGROUND

Drug enantiomers often display distinguishable or even opposite pharmacological and toxicologic activities. Therefore it is of great necessity to discriminate enantiomers for guaranteeing safetyness and effectiveness of chiral drugs. Facile chiral discrimination has long been a noticeable challenge because of the minimal differences in physicochemical properties of enantiomers. As one of high-performance chirality selection components, chiral metal-organic frameworks (CMOFs) are bringing new opportunities for the establishment of chiral discrimination platform with merits of high enantioselectivity, low cost, and facile operation.

RESULTS

By introducing D-Histidine as a modulator, a CMOFs material termed as D-Histidine-ZIF-8 was prepared on chitosan (CS) with an in-situ growth protocol. The positively charged CMOFs/CS hybrids were adsorbed onto negatively charged polystyrene microplate via electrostatic interaction to form a chiral discrimination interface. This interface can effectively adsorb 3,4-Dihydroxyphenylalanine (DOPA) enantiomers, and the adsorbed molecules can be quantitated based on their quenching behavior on the chemiluminescent (CL) signal of Co2+-catalyzed luminol-H2O2 reaction. The results of contact angle measurements and density functional theory calculations imply that CMOFs/CS have stronger affinity towards D-isomer than L-isomer. Thus the sensitivity for quantifying D-isomer is 2.93 times of that for L-isomer, demonstrating the enantioselectivity of the CMOFs/CS hybrids. The content of D-isomer in nonracemic mixtures of DOPA enantiomers and real samples were assayed with satisfactory results, showing the practicality of this method. The strategy also exhibited discrimination capacity for many other chiral molecules.

SIGNIFICANCE

The CMOFs/CS hybrids prepared with in-situ growth protocol display satisfactory selectivity for discriminating enantiomers. Due to usage of multi-well microplate platform, the method is anticipated to achieve high-throughput assay in the future work. This study paves a pathway for facile chiral discrimination based on a chemiluminescence quenching mode to meet the demand of drug development and manufacture.

A review of metal-organic frameworks and polymers in mixed matrix membranes for CO2 capture

Polymeric membranes offer an appealing solution for sustainable CO2 capture, with potential for large-scale deployment. However, balancing high permeability and selectivity is an inherent challenge for pristine membranes. To address this challenge, the development of mixed matrix membranes (MMMs) is a promising strategy. MMMs are obtained by carefully integrating porous nano-fillers into polymeric matrices, enabling the simultaneous enhancement of selectivity and permeability. In particular, metal-organic frameworks (MOFs) have gained recognition as MMM fillers for CO2 capture. Here, a review of the current state, recent advancements, and challenges in the fabrication and engineering of MMMs with MOFs for selective CO2 capture is proposed. Key considerations and promising research directions to fully exploit the gas separation potential of MOF-based MMMs in CO2 capture applications are highlighted.

Nano-Springe Enriched Hierarchical Porous MOP/COF Hybrid Aerogel: Efficient Recovery of Gold from Electronic Waste

Extraction of gold from secondary resources such as electronic waste (e-waste) has become crucial in recent times to compensate for the gradual scarcity of the noble metal in natural mines. However, designing and synthesizing a suitable material for highly efficient gold recovery is still a great challenge. Herein, we have strategically designed rapid fabrication of an ionic crystalline hybrid aerogel by covalent threading of an amino-functionalized metal-organic polyhedra with an imine-linked chemically stable covalent organic framework at ambient condition. The hierarchically porous ultra-light aerogel featuring imine-rich backbone, high surface area, and cationic sites have shown fast removal, high uptake capacity (2349 mg/g), and excellent selectivity towards gold sequestration. Besides, the aerogel can extract ultra-trace gold-ions from different terrestrial water bodies, aiming towards safe drinking water. This study demonstrates the great potential of the composite materials based on a novel approach to designing a hybrid porous material for efficient gold recovery from complex water matrices.

Host molecules inside metal-organic frameworks: host@MOF and guest@host@MOF (Matrjoschka) materials

The controllable encapsulation of host molecules (such as porphyrin, phthalocyanine, crown ether, calixarene or cucurbituril organic macrocycles, cages, metal-organic polyhedrons and enzymes) into the pores of metal-organic frameworks (MOFs) to form host-in-host (host@MOF) materials has attracted increasing research interest in various fields. These host@MOF materials combine the merits of MOFs as a host matrix and functional host molecules to exhibit synergistic functionalities for the formation of guest@host@MOF materials in sorption and separation, ion capture, catalysis, proton/ion conduction and biosensors. (This guest@host@MOF construction is reminiscent of Russian (Matrjoschka) dolls which are nested dolls of decreasing size placed one inside another.) In this tutorial review, the advantages of MOFs as a host matrix are presented; the encapsulation approaches and general important considerations for the preparation of host@MOF materials are introduced. The state-of-the-art examples of these materials based on different host molecules are shown, and representative applications and general characterization of these materials are discussed. This review will guide researchers attempting to design functional host@MOF and guest@host@MOF materials for various applications.

Alleviating hypoxia by integrating MnO2 with metal-organic frameworks coated upconversion nanocomposites for enhanced photodynamic therapy in vitro

Photodynamic therapy (PDT) requires the participation of abundant oxygen while the hypoxic tumor microenvironment limits the efficacy of PDT. Here, upconversion luminescent nanocomposites coated with metal-organic frameworks (MOFs) were synthesized and modified with MnO2 (named UMMnP) to alleviate hypoxia of the tumor microenvironment. Under 980 nm light irradiation, the upconversion nanoparticles (UCNPs) achieve upconversion emission to excite porphyrin MOFs, which then transfer energy to oxygen to produce singlet oxygen for PDT. At the same time, the MnO2 in the UMMnP nanocomposites can catalyze the generation of O2 from H2O2, which could increase singlet oxygen production in a hypoxic environment, thus enhancing the PDT effect. The HeLa cell viability assay shows that the UMMnP nanocomposites possess good biocompatibility, while after irradiation with 980 nm light, the cell viability decreases dramatically, demonstrating efficient PDT. Furthermore, the nanocomposites can be successfully applied for upconversion luminescence imaging in vitro. Thus, this work provides a promising application of bioimaging and enhanced photodynamic therapy by alleviating hypoxia in tumor treatment.

Recent advances in heterogeneous porous Metal-Organic Framework catalysis for Suzuki-Miyaura cross-couplings

Suzuki-Miyaura coupling (SMC), a crucial C-C cross-coupling reaction, is still associated with challenges such as high synthetic costs, intricate work-ups, and contamination with homogeneous metal catalysts. Research intensely focuses on strategies to convert homogeneous soluble metal catalysts into insoluble powder solids, promoting heterogeneous catalysis for easy recovery and reuse as well as for exploring greener reaction protocols. Metal-Organic Frameworks (MOFs), recognized for their high surface area, porosity, and presence of transition metals, are increasingly studied for developing heterogeneous SMC. The molecular fence effect, attributed to MOF surface functionalization, helps preventing catalyst deactivation by aggregation, migration, and leaching during catalysis. Recent reports demonstrate the enhanced catalytic activity, selectivity, stability, application scopes, and potential of MOFs in developing greener heterogeneous synthetic methodologies. This review focuses on the catalytic applications of MOFs in SMC reactions, emphasizing developments after 2016. It critically examines the synthesis and incorporation of active metal species into MOFs, focusing on morphology, crystallinity, and dimensionality for catalytic activity induction. MOF catalysts are categorized based on their metal nodes in subsections, with comprehensive discussion on Pd incorporation strategies, catalyst structures, optimal SMC conditions, and application scopes, concluding with insights into challenges and future research directions in this important emerging area of MOF applications.

Synthesis of highly sensitive and multi-response Eu-MOF, fluorescence sensing properties and anti-counterfeiting applications

A new Europium metal-organic framework (Eu-MOF), namely [Eu(dpa) (H2O)]·0.5(bpy)·4H2O}n (H4dpa = 5-(3,4-dicarboxyphenoxy) isophenic acid, bpy = protonated 4,4'-bipyridine) was synthesized and structurally characterized by elemental analyses, infrared spectroscopy, and X-ray single-crystal diffraction analyses. Eu-MOF shows a three-dimensional network structure based on EuIII ions and (dpa)4- ligands via µ4: η1, η2, η2, η2 coordination mode. Fluorescence analysis shows that Eu-MOF has excellent fluorescence sensing characteristics, which can efficiently and sensitively detect various pollutants in water: the limit of detection (LOD) of ratiometric fluorescence detection of ANI in water was 42.9 nM, which was better than the single-peak detection limit. In addition, the peak detection limits of Eu-MOF for Flu, ORN and NB were 120 nM, 27 nM and 94 nM, respectively. In addition, XPS, LUMO orbital energy level, fluorescence lifetime, ultraviolet absorption and other principles are used to explore the mechanism of fluorescence quenching. Surprisingly, Eu-MOF not only has excellent anti- counterfeiting ability and stability, can be used as anti-counterfeiting material in life, but also has good selectivity to Flu. Eu-MOF has obvious fluorescence quenching effect on Flu on paper under ultraviolet light, which can be used for rapid in situ imaging test paper of pesticide residues.

The Key to MOF Membrane Fabrication and Application: the Trade-off between Crystallization and Film Formation

Metal-organic frameworks (MOFs), owing the merits of ordered and tailored channel structures in the burgeoning crystalline porous materials, have demonstrated significant promise in construction of high-performance separation membranes. However, precisely because this crystal structure with strong molecular interaction in their lattice provides robust structural integrity and resistance to chemical and thermal degradation, crystalline MOFs typically exhibit insolubility, infusibility, stiffness and brittleness, and therefore their membrane-processing properties are far inferior to the flexible amorphous polymers and hinder their subsequent storage, transportation, and utilization. Hence, focusing on film-formation and crystallization is the foundation for exploring the fabrication and application of MOF membranes. In this review, the film-forming properties of crystalline MOFs are fundamentally analyzed from their inherent characteristics and compared with those of amorphous polymers, influencing factors of polycrystalline MOF membrane formation are summarized, the trade-off relationship between crystallization and membrane formation is discussed, and the strategy solving the film formation of crystalline MOFs in recent years are systematically reviewed, in anticipation of realizing the goal of preparing crystalline membranes with optimized processability and excellent performance.

Metal-phenolic network composites: from fundamentals to applications

Composites with tailored compositions and functions have attracted widespread scientific and industrial interest. Metal-phenolic networks (MPNs), which are composed of phenolic ligands and metal ions, are amorphous adhesive coordination polymers that have been combined with various functional components to create composites with potential in chemistry, biology, and materials science. This review aims to provide a comprehensive summary of both fundamental knowledge and advancements in the field of MPN composites. The advantages of amorphous MPNs, over crystalline metal-organic frameworks, for fabricating composites are highlighted, including their mild synthesis, diverse interactions, and numerous intrinsic functionalities. The formation mechanisms and state-of-the-art synthesis strategies of MPN composites are summarized to guide their rational design. Subsequently, a detailed overview of the chemical interactions and structure-property relationships of composites based on different functional components (e.g., small molecules, polymers, biomacromolecules) is provided. Finally, perspectives are offered on the current challenges and future directions of MPN composites. This tutorial review is expected to serve as a fundamental guide for researchers in the field of metal-organic materials and to provide insights and avenues to enhance the performance of existing functional materials in applications across diverse fields.

Pyrolytic Depolymerization of Polyolefins Catalysed by Zirconium-based UiO-66 Metal-Organic Frameworks

Polyolefins such as polyethylenes and polypropylenes are the most-produced plastic waste globally, yet are difficult to convert into useful products due to their unreactivity. Pyrolysis is a practical method for large-scale treatment of mixed, contaminated plastic, allowing for their conversion into industrially-relevant petrochemicals. Metal-organic frameworks (MOFs), despite their tremendous utility in heterogeneous catalysis, have been overlooked for polyolefin depolymerization due to their perceived thermal instabilities and inability of polyethylenes and polypropylenes to penetrate their pores. Herein, we demonstrate the viability of UiO-66 MOFs containing coordinatively-unsaturated zirconium nodes, as effective catalysts for pyrolysis that significantly enhances the yields of valuable liquid and gas hydrocarbons, whilst halving the amounts of residual solids produced. Reactions occur on the Lewis-acidic UiO-66 nodes, without the need for noble metals, and yield aliphatic product distributions distinctly different from the aromatic-rich hydrocarbons that can be obtained from zeolite catalysis. We also demonstrate the first unambiguous characterization of polyolefin penetration into UiO-66 pores at pyrolytic temperatures, allowing access to the abundant Zr-oxo nodes within the MOF interior for efficient C-C cleavage. Our work highlights the potential of MOFs as highly-designable heterogeneous catalysts for depolymerisation of plastics, which can complement conventional catalysts in reactivity.

A nanotrap infused ultrathin hybrid composite material for rapid and highly selective entrapment of 99TcO4. Chem Sci 2024:d4sc04010d. [PMID: 39430929 PMCID: PMC11485004 DOI: 10.1039/d4sc04010d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

99Tc is one of the potentially toxic radioactive substances owing to its long half-life and a high degree of environmental mobility. Hence, the sequestration of 99Tc from radioactive waste has become enormously important and a contemporary research priority. However, selective extraction of this species in its stable oxoanionic form (99TcO4 -) is very challenging on account of bottlenecks such as low charge density, less hydrophilic nature, etc. Herein, an ultrathin hybrid composite material has been strategically designed and fabricated by covalent anchoring of a chemically stable amino functionalized nanosized cationic metal-organic polyhedron with a positively charged robust ionic covalent organic framework. The resulting thin-layer-based hybrid composite presented multiple exfoliated exposed interactive sites, including a Zr(iv)-secondary building unit, amine and triaminoguanidine functional groups, which can selectively interact with TcO4 - oxoanions through a synergistic combination of electrostatic, H-bonding and various other supramolecular interactions. Thus synthesized function-tailored composite, by virtue of its multiple unique characteristics, manifested an ultrafast and very selective, high distribution coefficient (∼106 mL g-1), as well as recyclable entrapment of TcO4 - oxoanions from the complex mixture of superfluous (∼5000-fold) other interfering anions in both high and ultra-trace concentrations along with simulated nuclear waste and from different water systems. Dynamic flow-through experiments were conducted with the membrane of the hybrid material in simulated wastewater, which reduced the concentration of ReO4 - (surrogate of radioactive TcO4 -) to below the WHO permissible level with rapid sequestration kinetics and excellent selectivity over excessive competing anions.

Covalent Organic Frameworks for Electrocatalysis: Design, Applications, and Perspectives

Covalent organic frameworks (COFs) are an innovative class of crystalline porous polymers composed of light elements such as C, N, O, etc., linked by covalent bonds. The distinctive properties of COFs, including designable building blocks, large specific surface area, tunable pore size, abundant active sites, and remarkable stability, have led their widespread applications in electrocatalysis. In recent years, COF-based electrocatalysts have made remarkable progress in various electrocatalytic fields, including the hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, nitrogen reduction reaction, nitrate reduction reaction, and carbon dioxide reduction reaction. This review begins with an introduction to the design and synthesis strategies employed for COF-based electrocatalysts. These strategies include heteroatom doping, metalation of COF and building monomers, encapsulation of active sites within COF pores, and the development of COF-based derived materials. Subsequently, a systematic overview of the recent advancements in the application of COF-based catalysts in electrocatalysis is presented. Finally, the review discusses the main challenges and outlines possible avenues for the future development of COF-based electrocatalysts.

Extrinsically conducting MOFs: guest-promoted enhancement of electrical conductivity, thin film fabrication and applications

Conductive metal-organic frameworks are of current interest in chemical science because of their applications in chemiresistive sensing, electrochemical energy storage, electrocatalysis, etc. Different strategies have been employed to design conductive frameworks. In this review, we discuss the influence of different types of guest species incorporated within the pores or channels of metal-organic frameworks (MOFs) and porous coordination polymers (PCPs) to generate charge transfer pathways and modulate their electrical conductivity. We have classified dopants or guest species into three different categories: (i) metal-based dopants, (ii) molecule and molecular entities and (iii) organic conducting polymers. Different types of metal ions, metal nano-clusters and metal oxides have been used to enhance electrical conductivity in MOFs. Metal ions and metal nano-clusters depend on the hopping process for efficient charge transfer whereas metal-oxides show charge transport through the metal-oxygen pathway. Several types of molecules or molecular entities ranging from neutral TCNQ, I2, and fullerene to ionic methyl viologen, organometallic like nickelcarborane, etc. have been used. In these cases, the charge transfer process varies with the guest species. When organic conducting polymers are the guest, the charge transport occurs through the polymer chains, mostly based on extended π-conjugation. Here we provide a comprehensive and critical review of these strategies to add electrical conductivity to the, in most cases, otherwise insulating MOFs and PCPs. We point out the guest encapsulation process, the geometry and structure of the resulting host-guest complex, the host-guest interactions and the charge transport mechanism for each case. We also present the methods for thin film fabrication of conducting MOFs (both, liquid-phase and gas-phase based methods) and their most relevant applications like electrocatalysis, sensing, charge storage, photoconductivity, photocatalysis,… We end this review with the main obstacles and challenges to be faced and the appealing perspectives of these 21st century materials.

Reversible Molecule Interactions Enable Ultrastretchable and Recyclable Ionogels for Wearable Piezoionic Sensors

Ionogel-based piezoionic sensors feel motions and strains like human skin relying on reversible ion migrations under external mechanical stimulus and are of great importance to artificial intelligence. However, conventional ion-conductive polymers behave with degraded electrical and mechanical properties after thousands of strain cycles, and the discarded materials and devices become electronic wastes as well. Here, we develop ultrastretchable ionogels with superior electrical properties via the mediation of metal-organic frameworks, whose properties are attributed to reversible molecule interactions inside the material system. Ionogels present excellent mechanical properties with breaking elongation as high as 850%, exceeding most previously reported similar materials, and the high conductivity enables further application in sensor devices. In addition, our ionogels display superior recyclability because of the reversible physical and chemical interactions inside material molecules, which are eco-friendly to the environment. As a result, the ionogel-based piezoionic sensors deliver high sensitivity, flexibility, cyclic stability, and signal reliability, which are of great significance to wearable applications in human-motion detections such as throat vibration, facial expression, joint mobility, and finger movement. Our study paves the way for ultrastretchable and eco-friendly ionogel design for flexible electrochemical devices.

Design and development of metal-organic framework-based nanocomposite hydrogels for quantification of deferiprone in exhaled breath condensate

In this study, a novel fluorescence nanoprobe based on Materials of Institute Lavoisier (MIL-101) metal-organic frameworks embedding into the agarose hydrogel is fabricated using a hydrothermal technique. It uses for sensitive quantification of deferiprone in exhaled breath condensate (EBC) samples. The morphology and characterization of MIL-101/agarose nanocomposite hydrogel is studied by transmission electron microscopy, dynamic light scattering instrument, powder X-ray diffraction analysis, and Fourier transform infrared spectroscopy. The probe shows a reasonable fluorescence intensity quenching in the presence of deferiprone due to the interactions between iron centers in MIL-101 (Fe) and deferiprone, which likely form non-fluorescent complexes. The proposed nanoprobe demonstrates a linear calibration curve from 0.005 to 1.5 µg mL- 1 with a detection limit of 0.003 µg mL- 1. The intra- and inter-day precision of the reported method are 0.3% and 0.4% (n = 5, deferiprone concentration = 1.0 µg mL- 1), respectively. This method demonstrates high sensitivity and specificity towards deferiprone in the EBC samples and also presents a sensing platform with simplicity, convenience, fast implementation, and cost-effective in medical monitoring.

Metal-organic frameworks for organic transformations by photocatalysis and photothermal catalysis

Organic transformation by light-driven catalysis, especially, photocatalysis and photothermal catalysis, denoted as photo(thermal) catalysis, is an efficient, green, and economical route to produce value-added compounds. In recent years, owing to their diverse structure types, tunable pore sizes, and abundant active sites, metal-organic framework (MOF)-based photo(thermal) catalysis has attracted broad interest in organic transformations. In this review, we provide a comprehensive and systematic overview of MOF-based photo(thermal) catalysis for organic transformations. First, the general mechanisms, unique advantages, and strategies to improve the performance of MOFs in photo(thermal) catalysis are discussed. Then, outstanding examples of organic transformations over MOF-based photo(thermal) catalysis are introduced according to the reaction type. In addition, several representative advanced characterization techniques used for revealing the charge reaction kinetics and reaction intermediates of MOF-based organic transformations by photo(thermal) catalysis are presented. Finally, the prospects and challenges in this field are proposed. This review aims to inspire the rational design and development of MOF-based materials with improved performance in organic transformations by photocatalysis and photothermal catalysis.

Controllable Silver Release for Efficient Treatment of Drug-Resistant Bacterial-Infected Wounds

The use of traditional Ag-based antibacterial agents is usually accompanied by uncontrollable silver release, which makes it difficult to find a balance between antibacterial performance and biosafety. Herein, we prepared a core-shell system of ZIF-8-derived amorphous carbon-coated Ag nanoparticles (Ag@C) as an ideal research model to reveal the synergistic effect and structure-activity relationship of the structural transformation of carbon shell and Ag core on the regulation of silver release behavior. It is found that Ag@C prepared at 600 °C (AC6) exhibits the best ion release kinetics due to the combination of relatively simple shell structure and lower crystallinity of the Ag core, thereby exerting stronger antibacterial properties (>99.999 %) at trace doses (20 μg mL-1) compared with most other Ag-based materials. Meanwhile, the carbon shell prevents the metal Ag from being directly exposed to the organism and thus endows AC6 with excellent biocompatibility. In animal experiments, AC6 can effectively promote wound healing by inactivating drug-resistant bacteria while regulating the expression of TNF-α and CD31. This work provides theoretical support for the scientific design and clinical application of controllable ion-releasing antibacterial agents.

Comparative Study on the Proton Conduction Behaviors of Two Acidic Amphiphilic and Hydrophilic Coordination Compounds in Nafion Composite Membranes

The acidic amphiphilic compound H[Co(H2L1)(HL1)(phen)]·3H2O (H4(Co-L1), H3L1 = 5-(3', 5'-dicarboxylphenyl)-pyridine-2-carboxylic, phen = phenanthroline) and the hydrophilic compound [Ni(HL2)(H2O)5]·H2O (H(Ni-L2), H3L2 = 5-(3',5'-dicarboxylphenyl)-pyridine-3-carboxylic) were synthesized via hydrothermal reactions at acidic conditions. The acidity of H4(Co-L1) is stronger than of H(Ni-L2); while the hydrogen bond continuity in H4(Co-L1) extended monodirectionally, which is smaller compared to the three-directional extension observed in H(Ni-L2). The proton conduction behaviors of these two compounds as fillers of Nafion composite membranes have been investigated. The results indicate that the optimal doping amounts of H4(Co-L1) and H(Ni-L2) are 2 and 1%, respectively; the proton conductivities of H4(Co-L1)/Nafion-2 and H(Ni-L2)/Nafion-1 composite membranes are 0.243 and 0.212 S·cm-1, respectively, which are approximately 50.2 and 30.6% higher than that of pure Nafion membrane, respectively. A higher doping amount of H4(Co-L1) can be attributed to its hydrophobic phen ligand, which promotes compatibility with Nafion membrane and reduces aggregation. Hydrogen bond continuity has a more significant effect on proton conductivity than acidity at relatively low doping amounts; conversely, this relationship reverses at relatively high doping amounts.

Microporous Materials in Polymer Electrolytes: The Merit of Order

Solid-state batteries (SSBs) have garnered significant attention in the critical field of sustainable energy storage due to their potential benefits in safety, energy density, and cycle life. The large-scale, cost-effective production of SSBs necessitates the development of high-performance solid-state electrolytes. However, the manufacturing of SSBs relies heavily on the advancement of suitable solid-state electrolytes. Composite polymer electrolytes (CPEs), which combine the advantages of ordered microporous materials (OMMs) and polymer electrolytes, meet the requirements for high ionic conductivity/transference number, stability with respect to electrodes, compatibility with established manufacturing processes, and cost-effectiveness, making them particularly well-suited for mass production of SSBs. This review delineates how structural ordering dictates the fundamental physicochemical properties of OMMs, including ion transport, thermal transfer, and mechanical stability. The applications of prominent OMMs are critically examined, such as metal-organic frameworks, covalent organic frameworks, and zeolites, in CPEs, highlighting how structural ordering facilitates the fulfillment of property requirements. Finally, an outlook on the field is provided, exploring how the properties of CPEs can be enhanced through the dimensional design of OMMs, and the importance of uncovering the underlying "feature-function" mechanisms of various CPE types is underscored.

MOF-Based Membranes for Remediated Application of Water Pollution

Membrane separation plays a crucial role in the current increasingly complex energy environment. Membranes prepared by metal-organic framework (MOF) materials usually possess unique advantages in common, such as uniform pore size, ultra-high porosity, enhanced selectivity and throughput, and excellent adsorption property, which have been contributed to the separation fields. In this comprehensive review, we summarize various designs and synthesized strategies of free-standing MOF and composite MOF-based membranes for water treatment. Special emphases are given not only on the effects of MOF on membrane performance, removal efficiencies, and elimination mechanisms, but also on the importance of MOF-based membranes for the applications of oily and micro-pollutant removal, adsorption, separation, and catalysis. The challenges and opportunities in the future for the industrial implementation of MOF-based membranes are also discussed.

Mechanisms of the Accelerated Li+ Conduction in MOF-Based Solid-State Polymer Electrolytes for All-Solid-State Lithium Metal Batteries

Solid polymer electrolytes (SPEs) for lithium metal batteries have garnered considerable interests owing to their low cost, flexibility, lightweight, and favorable interfacial compatibility with battery electrodes. Their soft mechanical nature compared to solid inorganic electrolytes give them a large advantage to be used in low pressure solid-state lithium metal batteries, which can avoid the cost and weight of the pressure cages. However, the application of SPEs is hindered by their relatively low ionic conductivity. In addressing this limitation, enormous efforts are devoted to the experimental investigation and theoretical calculations/simulation of new polymer classes. Recently, metal-organic frameworks (MOFs) have been shown to be effective in enhancing ion transport in SPEs. However, the mechanisms in enhancing Li+ conductivity have rarely been systematically and comprehensively analyzed. Therefore, this review provides an in-depth summary of the mechanisms of MOF-enhanced Li+ transport in MOF-based solid polymer electrolytes (MSPEs) in terms of polymer, MOF, MOF/polymer interface, and solid electrolyte interface aspects, respectively. Moreover, the understanding of Li+ conduction mechanisms through employing advanced characterization tools, theoretical calculations, and simulations are also reviewed in this review. Finally, the main challenges in developing MSPEs are deeply analyzed and the corresponding future research directions are also proposed.

Chemical shaping of CPO-27-M (M = Co, Ni) through an in situ crystallization within chitosan hydrogels

The preparation of MOF composites is considered as an effective method to address the challenges of shaping MOFs and to create porous solids with enhanced properties and broader applications. In this study, CPO-27-Co was crystallized via a simple strategy within porous chitosan beads. The resulting CS@CPO-27-Co composites were tested for CO2 sorption and they demonstrated promising performances by exceeding 3 mmol(CO2) g-1. The versatility of this strategy was further demonstrated by replacing cobalt(II) ions with nickel(II), also leading to the isostructural CPO-27 framework.

Confinement-Induced Biocatalytic Activity Enhancement of Light- and Thermoresponsive Polymer@Enzyme@MOF Composites

Metal-organic frameworks (MOFs) are favorable hosting materials for fixing enzymes to construct enzyme@MOF composites and to expand the applications of biocatalysts. However, the rigid structure of MOFs without tunable hollow voids and a confinement effect often limits their catalytic activities. Taking advantage of the smart soft polymers to overcome the limitation, herein, a protection protocol to encapsulate the enzyme in zeolitic imidazolate framework-8 (ZIF-8) was developed using a glutathione-sensitive liposome (L) as a soft template. Glucose oxidase (GOx) and horseradish peroxidase (HRP) were first anchored on a light- and thermoresponsive porous poly(styrene-maleic anhydride-N,N-dimethylaminoethyl methacrylate-spiropyran) membrane (PSMDSP) to produce PSMDSP@GOx-HRP, which could provide a confinement effect by switching the UV irradiation or varying the temperature. Afterward, embedding PSMDSP@GOx-HRP in L and encapsulating PSMDSP@GOx-HRP@L into hollow ZIF-8 (HZIF-8) to form PSMDSP@GOx-HRP@HZIF-8 composites were performed, which proceeded during the crystallization of the framework following the removal of L by adding glutathione. Impressively, the biocatalytic activity of the composites was 4.45-fold higher than that of the free enzyme under UV irradiation at 47 °C, which could benefit from the confinement effect of PSMDSP and the conformational freedom of the enzyme in HZIF-8. The proposed composites contributed to the protection of the enzyme against harsh conditions and exhibited superior stability. Furthermore, a colorimetric assay based on the composites for the detection of serum glucose was established with a linearity range of 0.05-5.0 mM, and the calculated LOD value was 0.001 mM in a cascade reaction system. This work provides a universal design idea and a versatile technique to immobilize enzymes on soft polymer membranes that can be encapsulated in porous rigid MOF-hosts. It also holds potential for the development of smart polymer@enzyme@HMOFs biocatalysts with a tunable confinement effect and high catalytic performance.

Measuring Mass Transfer of n-Hexane and 2-Chloroethyl Ethyl Sulfide in Sorbent/Polymer Fiber Composites Using a Volumetric Adsorption Apparatus

The integration of metal-organic frameworks (MOFs) into composite systems serves as an effective strategy to increase the processability of these materials. Notably, MOF/fiber composites have shown much promise as protective equipment for the capture and remediation of chemical warfare agents. However, the practical application of these composites requires an understanding of their mass transport properties, as both mass transfer resistance at the surface and diffusion within the materials can impact the efficacy of these materials. In this work, we synthesized composite fibers of MOF-808 and amidoxime-functionalized polymers of intrinsic microporosity (PIM-1-AX) and measured the adsorption and mass transport behavior of n-hexane and 2-chloroethyl ethyl sulfide (CEES), a sulfur mustard simulant. We developed a new Fickian diffusion model for cylindrical shapes to fit the dynamic adsorption data obtained from a commercial volumetric adsorption apparatus and found that mass transport behavior in composite fibers closely resembled that in the pure PIM fibers, regardless of MOF loading. Moreover, we found that n-hexane adsorption mirrors that of CEES, indicating that it could be used as a structural mimic for future adsorption studies of the sulfur mustard simulant. These preliminary insights and the new model introduced in this work lay the groundwork for the design of next-generation composite materials for practical applications.

Rare [Cu4I2]2+ cationic cluster-based metal-organic framework and hierarchical porous composites design for effective detection and removal of roxarsone and antibiotics

Fluorescence quenching induced by photoinduced electron transfer (PET) stands as an effective strategy for identifying water pollutants. Herein, a novel (4, 8)-connected three-dimensional framework Cu(I)-MOF ([Cu2I(tpt)]n) with unique 8-connected [Cu4I2]2+ cationic clusters is designed by employing the nitrogen-rich ligand (Htpt = 5-[4(1H-1,2,4-triazol-1-yl)]phenyl-2H-tetrazole). Water-stabilized Cu(I)-MOF exhibits outstanding fluorescence properties, facilitating its application in detecting organic pollutants in water. Benefiting from the fact that the Cu(I)-MOF possesses a higher lowest unoccupied molecular orbitals (LUMO) energy level than that of the analyte, the rapid d-PET can occur, entitling Cu(I)-MOF to a sensitive fluorescence quenching response to roxarsone (ROX), nitrofurazone (NFZ) and nitrofurantoin (NFT) (with detection limits as low as 0.13 µM, 0.15 µM, and 0.13 µM, respectively). The nitrogen-containing sites of melamine foam (MF) are utilized to facilitate the anchoring and growth of Cu-MOF crystals, which enables the preparation of hierarchical microporous - macroporous Cu(I)-MOF/MF composites. The ordered porous structure of Cu(I)-MOF/MF provides cavities and open sites for the efficient removal of ROX (qmax = 210.6 mg∙g-1), NFZ (qmax = 111.5 mg∙g-1) and NFT (qmax = 238.9 mg∙g-1) from water. This characteristic endows the Cu(I)-MOF/MF with rapid and recyclable adsorption capacity. Therefore, this work provides valuable insights to address the problem of detection and removal of pollutants in the aquatic environment.

Three-Component Construction of Mesoporous Metal-Organic Frameworks and Their Incorporation into Solid Polymer Electrolytes for Li-Ion Conduction

Solid electrolytes with high ionic conductivity and satisfactory electrochemical stability are essential for the development of solid-state batteries. However, current strategies, including polymer (and polymer-based composite) electrolytes, still face challenges in meeting the bar set by real operations. We seek to improve the Li-ion conduction of the electrolytes by incorporating mesoporous metal-organic frameworks (MOFs) into the polymer matrix. Specifically, MOFs with pores larger than 3.0 nm are constructed by three-component reactions that involve the construction of both coordinative and dynamic imine linkages. The MOFs allow polymer penetration and amorphization and efficient lithium salt dissociation in the confined channels. Numerous metal sites and organic functionalities in the MOF backbone further assist the ion migration by providing strong interactions with the fluorinated polymer and the Li+. Remarkable ionic conductivity (0.95 mS cm-1) and a large lithium transference number (0.64) are achieved. Overall, the study fully utilizes both the MOF structural units with atomic precision and the encompassed space at the mesoscale for solid-state electrolyte development.

Application of metal-organic frameworks and their derivates for thermal-catalytic C1 molecules conversion

One-carbon (C1) catalysis refers to the conversion of compounds with a single carbon atom, especially carbon monoxide (CO), carbon dioxide (CO2), and methane (CH4), into clean fuels and valuable chemicals via catalytic strategy is crucial for sustainable and green development. Among various catalytic strategies, thermal-driven process seems to be one of the most promising pathways for C1 catalysis due to the high efficiency and practical application prospect. Notably, the rational design of thermal-driven C1 catalysts plays a vital role in boosting the targeted products synthesis of C1 catalysis, which relies heavily on the choice of ideal active site support, catalyst fabrication precursor, and catalytic reaction field. As a novel crystalline porous material, metal-organic frameworks (MOFs) has made significant progress in the design and synthesis of various functional nanomaterials. However, the application of MOFs in C1 catalysis faces numerous challenges, such as thermal stability, mechanical strength, yield of MOFs, and so on. To overcome these limitations and harness the advantages of MOFs in thermal-driven C1 catalysis, researchers have developed various catalyst/carrier preparation strategies. In this review, we provide a concise overview of the recent advancements in the conversion of CO, CO2, and CH4 into clean fuels and valuable chemicals via thermal-catalytic strategy using MOFs-based catalysts. Furthermore, we discuss the main challenges and opportunities associated with MOFs-based catalysts for thermal-driven C1 catalysis in the future.

Molecular-caged metal-organic frameworks for energy management

Metal-organic frameworks (MOFs) hold great promise for diverse applications when combined with polymers. However, a persistent challenge lies in the susceptibility of exposed MOF pores to molecule and polymer penetration, compromising the porosity and overall performance. Here, we design a molecular-caged MOF (MC-MOF) to achieve contracted window without sacrificing the MOF porosity by torsional conjugated ligands. These molecular cages effectively shield against the undesired molecule penetration during polymerization, thereby preserving the pristine porosity of MC-MOF and providing outstanding light and thermal management to the composites. The polymer containing 0.5 wt % MC-MOF achieves an 83% transmittance and an exceptional haze of 93% at 550 nanometers, coupled with remarkable thermal insulation. These MC-MOF/polymer composites offer the potential for more uniform daylighting and reduced energy consumption in sustainable buildings when compared to traditional glass materials. This work delivers a general method to uphold MOF porosity in polymers through molecular cage design, advancing MOF-polymer applications in energy and sustainability.

Construction of Hierarchical Porous UiO-66-Br2@PS/DVB-Packed Columns by High Internal Phase Emulsion Strategy for Enhanced Separation of CF4/N2 and SF6/N2

Recovery and separation of anthropogenic emissions of electronic specialty gases (F-gases, such as CF4 and SF6) from the semiconductor sector are of critical importance. In this work, the hierarchical porous UiO-66-Br2@PS/DVB-packed column was constructed by a high internal phase emulsions strategy. UiO-66-Br2@PS/DVB exhibits a superior selectivity of CF4/N2 (2.67) and SF6/N2 (3.34) predicted by the IAST due to the diffusion limitation in the micropore and the gas-framework affinity. Especially, UiO-66-Br2@PS/DVB showed significant CF4 and SF6 retention and enabled the successful separation of CF4/N2 and SF6/N2 with a resolution of 2.37 and 8.89, respectively, when used as a packed column in gas chromatography. Compared with the Porapak Q column, the HETP of the UiO-66-Br2@PS/DVB-packed column decreased and showed good reproducibility. This research not only offers a convenient method for fabricating a hierarchical porous MOF-packed column but also showcases the prospective utilization of MOFs for the separation of the F-gas/N2 mixture.

From nano- to macroarchitectures: designing and constructing MOF-derived porous materials for persulfate-based advanced oxidation processes

Persulfate-based advanced oxidation processes (PS-AOPs) have gained significant attention as an effective approach for the elimination of emerging organic contaminants (EOCs) in water treatment. Metal-organic frameworks (MOFs) and their derivatives are regarded as promising catalysts for activating peroxydisulfate (PDS) and peroxymonosulfate (PMS) due to their tunable and diverse structure and composition. By the rational nanoarchitectured design of MOF-derived nanomaterials, the excellent performance and customized functions can be achieved. However, the intrinsic fine powder form and agglomeration ability of MOF-derived nanomaterials have limited their practical engineering application. Recently, a great deal of effort has been put into shaping MOFs into macroscopic objects without sacrificing the performance. This review presents recent advances in the design and synthetic strategies of MOF-derived nano- and macroarchitectures for PS-AOPs to degrade EOCs. Firstly, the strategies of preparing MOF-derived diverse nanoarchitectures including hierarchically porous, hollow, yolk-shell, and multi-shell structures are comprehensively summarized. Subsequently, the approaches of manufacturing MOF-based macroarchitectures are introduced in detail. Moreover, the PS-AOP application and mechanisms of MOF-derived nano- and macromaterials as catalysts to eliminate EOCs are discussed. Finally, the prospects and challenges of MOF-derived materials in PS-AOPs are discussed. This work will hopefully guide the design and development of MOF-derived porous materials in SR-AOPs.

Nanocomposites Based on Magnetic Nanoparticles and Metal-Organic Frameworks for Therapy, Diagnosis, and Theragnostics

In the last two decades, metal-organic frameworks (MOFs) with highly tunable structure and porosity, have emerged as drug nanocarriers in the biomedical field. In particular, nanoscaled MOFs (nanoMOFs) have been widely investigated because of their potential biocompatibility, high drug loadings, and progressive release. To enhance their properties, MOFs have been combined with magnetic nanoparticles (MNPs) to form magnetic nanocomposites (MNP@MOF) with additional functionalities. Due to the magnetic properties of the MNPs, their presence in the nanosystems enables potential combinatorial magnetic targeted therapy and diagnosis. In this Review, we analyze the four main synthetic strategies currently employed for the fabrication of MNP@MOF nanocomposites, namely, mixing, in situ formation of MNPs in presynthesized MOF, in situ formation of MOFs in the presence of MNPs, and layer-by-layer methods. Additionally, we discuss the current progress in bioapplications, focusing on drug delivery systems (DDSs), magnetic resonance imaging (MRI), magnetic hyperthermia (MHT), and theragnostic systems. Overall, we provide a comprehensive overview of the recent advances in the development and bioapplications of MNP@MOF nanocomposites, highlighting their potential for future biomedical applications with a critical analysis of the challenges and limitations of these nanocomposites in terms of their synthesis, characterization, biocompatibility, and applicability.

Heterometallic MIL-125(Ti-Al) frameworks for electrochemical determination of ascorbic acid, dopamine and uric acid

The detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) is not only of great significance in the areas of biomedicine and neurochemistry but also helpful in disease diagnosis and pathology research. Due to their diverse structures, designability, and large specific surface areas, metal-organic frameworks (MOFs) have recently caught considerable attention in the electrochemical field. Herein, a family of heterometallic MOFs with amino modification, MIL-125(Ti-Al)-xNH2 (x = 0%, 25%, 50%, 75%, and 100%), were synthesized and employed as electrochemical sensors for the detection of AA, DA, and UA. Among them, MIL-125(Ti-Al)-75%NH2 exhibited the most promising electrochemical behavior with 40% doping of carbon black in 0.1 M PBS (pH = 7.10), which displayed individual detection performance with wide linear detection ranges (1.0-6.5 mM for AA, 5-100 μM for DA and 5-120 μM for UA) and low limits of detection (0.215 mM for AA, 0.086 μM for DA, and 0.876 μM for UA, S/N = 3). Furthermore, the as-prepared MIL-125(Ti-Al)-75%NH2/GCE provided a promising platform for future application in real sample analysis, owing to its excellent anti-interference performance and good stability.

Biomedical application of metal-organic frameworks (MOFs) in cancer therapy: Stimuli-responsive and biomimetic nanocomposites in targeted delivery, phototherapy and diagnosis

The nanotechnology is an interdisciplinary field that has become a hot topic in cancer therapy. Metal-organic frameworks (MOFs) are porous materials and hybrid composites consisted of organic linkers and metal cations. Despite the wide application of MOFs in other fields, the potential of MOFs for purpose of cancer therapy has been revealed by the recent studies. High surface area and porosity, significant drug loading and encapsulation efficiency are among the benefits of using MOFs in drug delivery. MOFs can deliver genes/drugs with selective targeting of tumor cells that can be achieved through functionalization with ligands. The photosensitizers and photo-responsive nanostructures including carbon dots and gold nanoparticles can be loaded in/on MOFs to cause phototherapy-mediated tumor ablation. The immunogenic cell death induction and increased infiltration of cytotoxic CD8+ and CD4+ T cells can be accelerated by MOF platforms in providing immunotherapy of tumor cells. The stimuli-responsive MOF platforms responsive to pH, redox, enzyme and ion can accelerate release of therapeutics in tumor site. Moreover, MOF nanocomposites can be modified ligands and green polymers to improve their selectivity and biocompatibility for cancer therapy. The application of MOFs for the detection of cancer-related biomarkers can participate in the early diagnosis of patients.

Tannic acid and carboxymethyl chitosan-based multi-functional double-layered hydrogel with pH-stimulated response behavior for smart real-time infection monitoring and wound treatment

The dramatic increase of drug-resistant pathogenic bacteria has seriously effect on human health, appealing the needs of developing theranostic platforms with stimuli-responsive materials to realize the accurate bacterial diagnostics and therapeutics. Herein, a tannic acid and carboxymethyl chitosan-based multifunctional ZIF-90@i-PPOPs-phenol red double-layered hydrogel with stimuli-responsiveness and antibacterial activity was fabricated. The inner layer hydrogel (ZIF-90@i-PPOPs-based TFC hydrogels) was fabricated based on ZIF-90@i-PPOPs, integrate tannic acid and carboxymethyl chitosan linked by formylphenylboronic acid (FPBA), which exhibited outstanding injectable, biodegradability and antibacterial activity. The outer layer hydrogel (PR@PAM hydrogels) were constructed from polyacrylamide (PAM) and pH indicator phenol red, owning porous structure and excellent tissue adhesion. Due to the weakly acidic microenvironment within wound, the inner-layer hydrogel was stimulus-responsively decomposed, resulting in the accurate delivery of the positively charged ZIF-90@i-PPOPs to the lesion site to capture and kill bacteria by enhanced Zn2+ and ROS release. Meantime, the outer-layer hydrogel could real-timely monitor the pH changes to evaluate the wound recovery status. These double-layered hydrogels possessed precisely pH monitoring capacity, excellent antibacterial ability and negligible side effect to normal tissue in vivo, implying the high potential of the suggested hydrogels as theranostic platform for antibacterial treatment.

2D Materials Nanoarchitectonics for 3D Structures/Functions

It has become clear that superior material functions are derived from precisely controlled nanostructures. This has been greatly accelerated by the development of nanotechnology. The next step is to assemble materials with knowledge of their nano-level structures. This task is assigned to the post-nanotechnology concept of nanoarchitectonics. However, nanoarchitectonics, which creates intricate three-dimensional functional structures, is not always easy. Two-dimensional nanoarchitectonics based on reactions and arrangements at the surface may be an easier target to tackle. A better methodology would be to define a two-dimensional structure and then develop it into a three-dimensional structure and function. According to these backgrounds, this review paper is organized as follows. The introduction is followed by a summary of the three issues; (i) 2D to 3D dynamic structure control: liquid crystal commanded by the surface, (ii) 2D to 3D rational construction: a metal-organic framework (MOF) and a covalent organic framework (COF); (iii) 2D to 3D functional amplification: cells regulated by the surface. In addition, this review summarizes the important aspects of the ultimate three-dimensional nanoarchitectonics as a perspective. The goal of this paper is to establish an integrated concept of functional material creation by reconsidering various reported cases from the viewpoint of nanoarchitectonics, where nanoarchitectonics can be regarded as a method for everything in materials science.

Ultralight crystalline hybrid composite material for highly efficient sequestration of radioiodine

Considering the importance of sustainable nuclear energy, effective management of radioactive nuclear waste, such as sequestration of radioiodine has inflicted a significant research attention in recent years. Despite the fact that materials have been reported for the adsorption of iodine, development of effective adsorbent with significantly improved segregation properties for widespread practical applications still remain exceedingly difficult due to lack of proper design strategies. Herein, utilizing unique hybridization synthetic strategy, a composite crystalline aerogel material has been fabricated by covalent stepping of an amino-functionalized stable cationic discrete metal-organic polyhedra with dual-pore containing imine-functionalized covalent organic framework. The ultralight hybrid composite exhibits large surface area with hierarchical macro-micro porosity and multifunctional binding sites, which collectively interact with iodine. The developed nano-adsorbent demonstrate ultrahigh vapor and aqueous-phase iodine adsorption capacities of 9.98 g.g-1 and 4.74 g.g-1, respectively, in static conditions with fast adsorption kinetics, high retention efficiency, reusability and recovery.

Dual Stimulus-Responsive Enzyme@Metal-Organic Framework-Polymer Composites toward Enhanced Catalytic Performance for Visual Detection of Glucose

Enzyme immobilization on a metal-organic framework (enzyme@MOF) has been proven to be a promising strategy for boosting catalysis and biosensing applications. However, promoting the catalytic performance of polymer-modified enzyme@MOF composites remains an ongoing challenge. Herein, a protocol for enzyme immobilization was designed by using a smart polymer-modified MOF (UiO-66-NH2, UN) as the support. Through in situ polymerization, the dual stimulus-responsive poly(N-2-dimethylamino ethyl methacrylate) (PDM) was prepared. The PDM as a "soft cage" protected the immobilized glucose oxidase (GOx)-horseradish peroxidase (HRP) on the surface of the rigid UN. The confinement effect was generated by varying the temperature and pH, thereby improving the catalytic activity of the GOx-HRP@UN-PDM composites. In comparison with free enzymes, the fabricated composites exhibited an 8.9-fold enhancement in catalytic performance (Vmax) at pH 5.0 and 49 °C. Furthermore, relying on a cascade reaction generated in the composites, an assay was developed for the visual detection of glucose in rat serum. This study introduces a groundbreaking approach for the construction of smart enzyme@MOF-polymer composites with high catalytic activity for sensitive monitoring of biomolecules.

Role of Interface of Metal-Organic Frameworks and Their Composites in Persulfate-Based Advanced Oxidation Process for Water Purification

The persulfate activation-based advanced oxidation process (PS-AOP) is an important technology in wastewater purification. Using metal-organic frameworks (MOFs) as heterogeneous catalysts in the PS-AOP showed good application potential. Considering the intrinsic advantages and disadvantages of MOF materials, combining MOFs with other functional materials has also shown excellent PS activation performance and even achieves certain functional expansion. This Review introduces the classification of MOFs and MOF-based composites and the latest progress of their application in PS-AOP systems. The relevant activation/degradation mechanisms are summarized and discussed. Moreover, the importance of catalyst-related interfacial interaction for developing and optimizing advanced oxidation systems is emphasized. Then, the interference behavior of environmental parameters on the interfacial reaction is analyzed. Specifically, the initial solution pH and coexisting inorganic anions may hinder the interfacial reaction process via the consumption of reactive oxygen species, affecting the activation/degradation process. This Review aims to explore and summarize the interfacial mechanism of MOF-based catalysts in the activation of PS. Hopefully, it will inspire researchers to develop new AOP strategies with more application prospects.