Metal-Organic Framework Based Dielectric Layer Toward Highly Improving Triboelectric Charge Generation Properties

Triboelectric nanogenerator (TENG) as an environmental energy recovery and harvesting technology has attracts much attention. However, the improvement of TENG's output performance becomes one of the core issues. And the modification of triboelectric materials may be an effective approach. Here, two metal-organic framework (MOF) materials namely TIFSIX-2-Cu-i and Cu(Qc)2 are synthesized, and the influence of different organic ligands on the electromechanical conversion of TENG is investigated by starting from the intrinsic structure of MOFs. With the polydimethylsiloxane (PDMS)@TIFSIX-2-Cu-I and PDMS@Cu(Qc)2 triboelectric layer, the electrical output of the TENG increases by 4.5 times and 3 times, respectively. Meanwhile, a double dielectric layer composite structure is proposed to further improve the performance of TENG. Accordingly, the MOF-TENG with a double dielectric layer shows a maximum power density of 0.12 mW cm-2, which is 6.3 times than that of the original TENG. Based on the designed energy management circuit, the MOF-TENG exhibits good energy supply capability which can sustainably power small electronics just by harvesting human mechanical energy. This work proposes a new strategy to improve the performance of TENG and may promote the development of self-powered electronics or systems.

Photoclick surface modification of MOF-808 for galactose-mediated targeted chemotherapy

Controllable surface modification of nanoparticulate drug delivery vectors is key to enhancing specific desirable properties such as colloidal stability, targeting, and stimuli-responsive cargo release. Metal-organic frameworks (MOFs) have been proposed as potential delivery devices, with surface modification achieved by various bioconjugate "click" reactions, including copper-catalysed and strain-promoted azide-alkyne cycloaddition. Herein, we show that photo-induced nitrile imine-mediated tetrazole-ene cycloaddition (NITEC) can be used to surface-modify tetrazole-appended Zr MOFs with maleimides, and vice versa, with the extent of this traceless surface functionalisation controlled by the length of photoirradiation. This "photoclick" surface modification protocol is exemplified by the decorating of carboplatin-loaded MOF-808 with galactose units to target asialoglycoprotein receptors of specific cancer cell types. Targeting towards HepG2 cells, which overexpress these receptors, is indicated by enhanced endocytosis and cytotoxicity in both two- and three-dimensional cell cultures compared to other cell lines. The study shows both the power of the NITEC protocol for functionalisation of MOFs, and also the benefits of carbohydrate targeting in drug delivery vectors, with scope for significant additional work diversifying the surface targeting units available for nanoparticle functionalisation under these mild, biocompatible "photoclick" conditions.

Synthesis of hierarchical ZIF-8/carbon nanotube structure via zinc hydroxide nanostrands as a butanol QCM nanosensor

A composite of ZIF-8 metal organic framework/multi-walled carbon nanotube (MWCNT) was synthesized at room temperature using zinc hydroxide nanostrands (ZHNSs) as the metal source. ZHNS not only served as a metal source but also acted as a template, confining the nucleation and growth of ZIF-8 on the MWCNT. This led to the low linker/metal ion molar ratio necessary for ZIF-8 synthesis. The resulting composite was used in the fabrication of a quartz crystal microbalance (QCM) nanosensor for detecting volatile organic compounds (VOCs). The nanosensor was assessed in a N2 atmosphere with various VOCs, including n-hexane, n-pentane, acetone, ethanol, methanol, methyl butanol, and butanol at different concentrations. Among these VOCs, the sensor displayed the most significant response to butanol, showing a sensitivity of 2.20 Hz ppm-1.

Decoding Framework Dynamics in a Spin Crossover Flexible Metal-Organic Framework

Functional spin crossover (SCO) metal-organic frameworks (MOFs) hold promise for miniaturized spin-based devices due to their tuneable molecule-based properties near room temperature. SCO describes the phenomenon where transition metal ions switch between high spin (HS) and low spin (LS) states upon external stimuli. However, even simple guest molecules like water can significantly alter the properties of these materials. Understanding the interplay between SCO and these molecules is therefore crucial. This work investigates this interplay in a fascinating 3D Fe(II) SCO-MOF, recently reported to exhibit reversible conductivity even in bulk. A combined experimental and computational approach is employed to explore how guest molecule uptake/release influences SCO dynamics including a transition from partial HS/LS to a fully LS state at high temperatures, (named reverse SCO) and ligand disorder-order behavior. The findings reveal a solid-state mechanism that differs from those previously described.

Metal-Organic Frameworks as a Thermal Emitter for High-Performance Passive Radiative Cooling

Passive radiative cooling represents a transformative approach to achieving sustainable cooling on Earth without relying on energy consumption. In this research, the optical characteristics of five readily accessible metal-organic frameworks (MOFs): ZIF-67(Co), MOF-74(Ni), HKUST-1(Cu), MOF-801(Zr), and UiO-66(Zr) are meticulously explored. The objective is to identify the pivotal factors that influence their ability to facilitate radiative cooling. Through an in-depth analysis encompassing spectroscopic features, surface texture, and porosity, it is found that the MOFs' cooling efficacy is largely influenced by their optical bandgaps and functional groups, although other factors like chemical composition and structural characteristics remain to be considered. Notably, UiO-66(Zr) emerged as the standout performer, boasting an impressive solar reflectance of 91% and a mid-infrared emissivity of 96.8%. Remarkably, a fabric treated with UiO-66(Zr) achieved a substantial sub-ambient cooling effect, lowering temperatures by up to 5 °C and delivering a cooling power of 26 W m-2 at 300 K. The findings underscore the vast potential of MOFs in offering new opportunities to advance passive radiative cooling technologies, paving the way for their extensive application in this field.

From Nanozymes to Multi-Purpose Nanomaterials: The Potential of Metal-Organic Frameworks for Proteomics Applications

Metal-organic frameworks (MOFs) have the potential to revolutionize the biotechnological and medical landscapes due to their easily tunable crystalline porous structure. Herein, the study presents MOFs' potential impact on proteomics, unveiling the diverse roles MOFs can play to boost it. Although MOFs are excellent catalysts in other scientific disciplines, their role as catalysts in proteomics applications remains largely underexplored, despite protein cleavage being of crucial importance in proteomics protocols. Additionally, the study discusses evolving MOF materials that are tailored for proteomics, showcasing their structural diversity and functional advantages compared to other types of materials used for similar applications. MOFs can be developed to seamlessly integrate into proteomics workflows due to their tunable features, contributing to protein separation, peptide enrichment, and ionization for mass spectrometry. This review is meant as a guide to help bridge the gap between material scientists, engineers, and MOF chemists and on the other side researchers in biology or bioinformatics working in proteomics.

Metal-organic framework-based smart stimuli-responsive drug delivery systems for cancer therapy: advances, challenges, and future perspectives

Cancer treatment is currently one of the most critical healthcare issues globally. A well-designed drug delivery system can precisely target tumor tissues, improve efficacy, and reduce damage to normal tissues. Stimuli-responsive drug delivery systems (SRDDSs) have shown promising application prospects. Intelligent nano drug delivery systems responsive to endogenous stimuli such as weak acidity, complex redox characteristics, hypoxia, active energy metabolism, as well as exogenous stimuli like high temperature, light, pressure, and magnetic fields are increasingly being applied in chemotherapy, radiotherapy, photothermal therapy, photodynamic therapy, and various other anticancer approaches. Metal-organic frameworks (MOFs) have become promising candidate materials for constructing SRDDSs due to their large surface area, tunable porosity and structure, ease of synthesis and modification, and good biocompatibility. This paper reviews the application of MOF-based SRDDSs in various modes of cancer therapy. It summarizes the key aspects, including the classification, synthesis, modifications, drug loading modes, stimuli-responsive mechanisms, and their roles in different cancer treatment modalities. Furthermore, we address the current challenges and summarize the potential applications of artificial intelligence in MOF synthesis. Finally, we propose strategies to enhance the efficacy and safety of MOF-based SRDDSs, ultimately aiming at facilitating their clinical translation.

Local order, disorder, and everything in between: using 91Zr solid-state NMR spectroscopy to probe zirconium-based metal-organic frameworks

Characterization of metal centers in metal-organic frameworks (MOFs) is critical for rational design and further understanding of structure-property relationships. The short-range structure about Zr atoms is challenging to properly elucidate in many Zr MOFs, particularly when local disorder is present. Static 91Zr solid-state NMR spectra of the seven zirconium MOFs UiO-66, UiO-66-NH2, UiO-67, MOF-801, MOF-808, DUT-68 and DUT-69 have been acquired at high magnetic fields of 35.2 T and 19.6 T, yielding valuable information on the local structure, site symmetry and order about Zr. 91Zr NMR is very sensitive to differences in MOF short-range structure caused by guest molecules, linker substitution and post-synthetic treatment. Complementary density functional theory (DFT) calculations assist in the interpretation and assignment of 91Zr solid-state NMR spectra, lend insight into structural origins of 91Zr NMR parameters and enable determination of local Zr coordination environments. This approach can be extended to many other materials containing zirconium.

Thorium metal-organic framework crystallization for efficient recovery from rare earth element mixtures

Rare earth (RE) elements are critical materials that underpin many modern technologies, particularly in the clean energy industry. Despite their importance, these vital resources are difficult to obtain due to the presence of numerous metals and radioactive contaminants, such as thorium, that are present in RE ores. Current processing methods, which are dominated by homogeneous solvent extraction, are inefficient and produce substantial hazardous waste. In this work, we describe an alternative strategy to separate thorium from REs through metal-organic framework (MOF) crystallization. Starting from a mixture of thorium and rare earth ions in solution, we utilize the simple carboxylate ligand trimesic acid to selectively crystallize a novel thorium MOF, NU-2500, leaving the remaining rare earth ions in solution. By leveraging the increased oxophilicity of Th(iv) compared to RE(iii) ions, we observe the exclusive formation of the thermodynamically preferred Th-MOF product. This valence-selective crystallization strategy occurs rapidly (within 30 minutes) at mild temperatures (80 °C) with an environmentally-friendly ethanol/water solvent system to produce phase-pure NU-2500 containing >98% molar fraction of thorium. Sequestering the radioactive Th(iv) ions within a solid framework enables facile separation of REs through simple filtration. We demonstrate that our selective crystallization platform retains its high selectivity for Th crystallization even at low initial Th concentrations and in complex mixtures with multiple different REs. We anticipate that further insights into the kinetics and thermodynamics of MOF crystallization can be applied to additional challenging industrial separations.

Synthesis of Selenized Metal-Organic Framework Hollow Cage under Ambient Condition for Clean Energy Applications

The synthesis of structured metal organic framework (MOF)-derived selenide composites is a vibrantly emerging research area serving clean energy purposes. However, there is no way to convert MOFs into structured selenide composites under ambient conditions for unknown reasons. This work gave mechanistic insights into how the redox properties and release rate of selenium precursors influenced the structural inheritance behavior of MOFs during the selenization process, explaining why maintaining the morphology of MOFs during a room-temperature aqueous selenization process is a tricky task. A novel method of selenizing structured ZIF-67 into CoSex hollow cages with its cubic morphology maintained was developed. The target combination between Co and Se was the primary mechanism accounting for ZIF-67 selenization and its morphology inheritance. The selenized ZIF-67 was used in two typical clean energy areas, i.e., coal combustion detoxification and renewable energy storage. The performances of selenized ZIF-67 surpassed those of unstructured cobalt selenides and other benchmark materials used in these two areas. Following the mechanistic insights into the selenization process of ZIF-67, further work may develop more efficient methods to synthesize MOF-derived metal selenide composites under mild conditions, which is critical to extend the variety of MOF-derived materials and serve their cost-effective uses under practical scenarios.

Enhancing Selective Hydrofluorocarbon Greenhouse Gas Capture via Halogenation of Metal-Organic Frameworks

Hydrofluorocarbons (HFCs) are anthropogenically produced greenhouse gases with longer atmospheric lifetimes and higher global warming potentials than those of carbon dioxide. General strategies to abate their emissions from industrial point sources, such as via adsorptive capture, remain scarce. Herein, we uncover the key structure-property relationships that lead to strong binding of HFCs such as fluoroform (CHF3) and difluoromethane (CH2F2) in metal-organic frameworks (MOFs) under the low pressures relevant to flue gas scrubbing. Extensive gas sorption and computational studies support that the Zr-based microporous framework MOF-801-Br or HHU-2-Br (HHU = Heinrich-Heine-University Düsseldorf) strongly binds HFCs due to its synergistic combination of Zr-OH sites on the nodes and bromine sites on the linkers. As such, MOF-801-Br demonstrates a record-setting performance for separating CHF3 from N2 under dilute conditions. Our work highlights that the combination of multiple hydrogen-bonding sites in microporous MOFs represents a generalizable strategy for HFC capture, enabling their selective removal from industrial waste streams.

Vapor-Deposited MOF for Low-k Dielectric Seamless High-Aspect-Ratio Interconnect Gap Fill

A vapor-phase ZIF-8 MOF deposition procedure for seamless high-aspect-ratio interconnect gap fill has been developed with a short process time (15 min) at a 160 °C process temperature. This is the most rapid documented vapor technique to produce a MOF film and is made possible by a higher process temperature and a low background H2O environment. The process consists of ALD of a thin (<5 nm) ZnO film followed by conversion to ZIF-8 in an organic linker (ALD + soak cycle). This method exhibited complete ZnO to MOF conversion, as well as MOFs with low-k (k ∼ 2.6). Dielectric gap fill was investigated utilizing patterned samples with widths ranging from 40 to 400 nm. Both high aspect ratio gap fill and multiple aspect ratio gap fills were shown with no residual ZnO. The MOF gap-fill process could be attributed to the reflow behavior of 2-methylimidazole-ZnO reaction intermediates or nascent product. The MOF was found to be stable at 400 °C under vacuum (1 × 10-2 Torr), which is comparable to other low-k dielectrics. Fluorine plasma etch resistance was tested for the ZIF-8 MOF in comparison to bare Si, SiCOH, and SiO2; the MOF was proven to be the best in resisting plasma etch. This work demonstrated that ALD + soak cycle conversion low-k ZIF-8 MOF films have the potential to be a plasma-free vapor-phase seamless gap fill for high aspect ratio features to be employed in logic and memory device fabrication, as well as three-dimensional heterogeneous integration (3DHI).

Mechanistic Insights into Solvent-Mediated Halide-Specific Irreversible Transformation of Cu-MOF with Iodide Detection Capability

The fascinating feature of metal-organic frameworks is that they can respond to external stimuli, unlike other inorganic materials. This feature corresponds to the framework's flexibility, which originates with the long-range crystalline order of the framework accompanied by cooperative structural transformability. We have synthesized a novel metal-organic framework comprised of Cu(I) nodes with pyrazine linkers and benzene-1,3,5-tricarboxylate acting as template anions, named CUCAM-1 [Cu(Py)2(BTC)]n. In the presence of polar solvent systems, CUCAM-1 undergoes an irreversible structural transformation to yield a mixed phase that consists of HKUST-1 [Cu3(BTC)2(H2O)3]n and another CUCAM-2 [Cu(Py)(BTC)]n MOFs, whose novel structure is successfully revealed by continuous rotation electron diffraction from the mixture. In this structural transformation, a new ligand exchange occurs where template anions become ligands, confirmed by single crystal X-ray analysis. Further, structural transformation and the mechanism are explained by ab initio molecular dynamics (AIMD) simulations. Interestingly, different halides (F-, Cl-, and Br-) can be accompanied to affect/control the composition of the second phase by favoring the formation of the HKUST-1 phase over CUCAM-2, which was evident by the powder X-ray diffraction studies. Furthermore, the structural transformation induced by I- resulted in a colorimetric response due to the formation of a new MOF CUCAM-3, paving the way for use as an iodide detector.

Mechanical properties of two-dimensional material-based thin films: a comprehensive review

Two-dimensional (2D) materials are materials with a thickness of one or a few atoms with intriguing electrical, chemical, optical, electrochemical, and mechanical properties. Therefore, they are deemed candidates for ubiquitous engineering applications. Films and three-dimensional (3D) structures made from 2D materials introduce a distinct assembly structure that imparts the inherent properties of pristine 2D materials on a macroscopic scale. Acquiring the adequate strength and toughness of 2D material structures is of great interest due to their high demand for numerous industrial applications. This work presents a comprehensive review of the mechanical properties and deformation behavior of robust films composed of 2D materials that help them to attain other extraordinary properties. Moreover, the various key factors affecting the mechanical performance of such thin films, such as the lateral size of nanoflakes, fabrication technique of the film, thickness of the film, post-processing, and strain rate, are elucidated.

Multiple Structural and Phase Transformations of MOF and Selective Hydrocarbon Gas Separation in its Amorphous, Glass Phase States

The first wide-view image of multiple structural and phase transformations for MOFs, ranging from crystal state transformations to the extreme limit approaching liquid/glass phase, was presented. The process involves i) an initial crystalline transformation from square-layer framework [Co2(pybz)2(CH3COO)2] ⋅ DMF (Co2) to a 3-fold interpenetrated and ordered vacancies contained framework [Co(pybz)2(CH3OH)2] ⋅ 2CH3OH (CoM) due to in situ disassemble-reassemble, ii) thermal induced departure of a pair of cis-form coordinated methanol in CoM leads to amorphous framework a-dCoM, iii) glass transition to super-cooled liquid scl-dCoM, iv) obtaining MOF glass g-dCoM upon quenching the super-cooled liquid, and v) re-crystallization of super-cooled liquid generates 6-fold interpenetrated dia-net framework [Co(pybz)2]6n (rec-dCoM) under further heating. The access to glass from CoM, provides a new self-perturbation strategy to create MOF glasses without melting. The wider pore size distribution in amorphous/glassy MOFs than crystalline precursor achieved the first time selective hydrocarbon gas separation by breakthrough experiments, which bring efficient separation of 1 : 99 C2H2/C2H4 by either a-dCoM or g-dCoM and produce polymer grade C2H4 with purity≥99.5 % after a single adsorption process. Furthermore, the mixture of 50 : 50 C3H6/C3H8 can be separated by a-dCoM.

Phase-dependent electronic structure modulation of nickel selenides by Fe doping for enhanced bifunctional oxygen electrocatalysis

Bifunctional oxygen electrocatalysis is a pivotal process that underpins a diverse array of sustainable energy technologies, including electrolyzers and fuel cells. Metal selenides have been identified as highly promising candidates for oxygen electrocatalysts with electronic structure engineering that lies at the heart of catalyst design. Two-phase Fe-doped nitrogen carbon (NC)-supported nickel selenides were synthesized using a coordination polymer template. Fe doping offers significant advantages as it enhances electronic interactions, resulting in higher availability of active sites than nickel selenides and optimizing the adsorption energy for reaction intermediates. Owing to the intriguing compositional and structural features, the obtained NixFe1-xSe2-NC@400 electrocatalyst displays better catalytic activity with an overpotential (η10) of 253 mV and a lower Tafel slope of 57.1 mV dec-1 for the Oxygen Evolution Reaction (OER) in 1 M KOH. Likewise, the catalyst demonstrated remarkable efficiency in Oxygen Reduction Reaction (ORR) catalysis, achieving a limiting current density comparable to that of the standard Pt/C catalyst and exhibiting an improved Tafel slope of 35.4 mV dec-1 in 0.1 M KOH. This work reveals the influence of Fe dopants in oxygen electrocatalysis and presents an effective approach to tuning the electronic structure for the development of highly active electrocatalysts in alkaline media.

Type III Porous Liquids Based on MOF-Derived Carbon for CO2 Capture

Type III porous liquids (T3PLs), which combine the benefits of solids and liquids, have gained attention for CO2 emission reduction and sustainable development. A key challenge is maintaining porosity by using small-pore-sized pore generators while avoiding the loss of porosity during dispersion in solvents. Traditional methods require complex postsynthetic modifications, which can compromise structural integrity and stability. In this study, MOF-5 with varying particle sizes was used as a carbon precursor to examine the impact of the particle size on metal-organic framework (MOF)-derived carbons. MCMOF-5, with an internal cubic cavity and a surface-dense graphene layer, was dispersed in poly(dimethylsiloxane) (PDMS) to prepare the T3PLs. MCM-410-3%, formed by MCMOF-5 and PDMS410, exhibited excellent CO2 sorption (1.89 mmol/g at 10.0 bar, 298 K) and cyclic stability, benefiting from well-developed carbon pores and protective graphite layers. Additionally, it maintains a low viscosity (108 mPa·s) and low density (0.551 g/cm3). This simple strategy of enhancing porous solid interfaces through calcination offers a new approach to the preparation of T3PLs and provides a new option for the use of CO2 capture materials.

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.

Heterogeneous Frustrated Lewis Pair Catalysts: Rational Structure Design and Mechanistic Elucidation Based on Intrinsic Properties of Supports

ConspectusThe discovery of reversible hydrogenation using metal-free phosphoborate species in 2006 marked the official advent of frustrated Lewis pair (FLP) chemistry. This breakthrough revolutionized homogeneous catalysis approaches and paved the way for innovative catalytic strategies. The unique reactivity of FLPs is attributed to the Lewis base (LB) and Lewis acid (LA) sites either in spatial separation or in equilibrium, which actively react with molecules. Since 2010, heterogeneous FLP catalysts have gained increasing attention for their ability to enhance catalytic performance through tailored surface designs and improved recyclability, making them promising for industrial applications. Over the past 5 years, our group has focused on investigating and strategically modifying various types of solid catalysts with FLPs that are unique from classic solid FLPs. We have explored systematic characterization techniques to unravel the underlying mechanisms between the active sites and reactants. Additionally, we have demonstrated the critical role of catalysts' intrinsic electronic and geometric properties in promoting FLP formation and stimulating synergistic effects. The characterization of FLP catalysts has been greatly enhanced by the use of advanced techniques such as synchrotron X-ray diffraction, neutron powder diffraction, X-ray photoelectron spectroscopy, extended X-ray absorption fine structure, elemental mapping in scanning transmission electron microscopy, electron paramagnetic resonance spectroscopy, diffuse-reflectance infrared Fourier transform spectroscopy, and solid-state nuclear magnetic resonance spectroscopy. These techniques have provided deeper insights into the structural and electronic properties of FLP systems for the future design of catalysts.Understanding electron distribution in the overlapping orbitals of LA and LB pairs is essential for inducing FLPs in operando in heterogeneous catalysts through target electron reallocation by external stimuli. For instance, in silicoaluminophosphate-type zeolites with weak orbital overlap, the adsorption of polar gas molecules leads to heterolytic cleavage of the Alδ+-Oδ- bond, creating unquenched LA-LB pairs. In a Ru-doped metal-organic framework, the Ru-N bond can be polarized through metal-ligand charge transfer under light, forming Ru+-N- pairs. This activation of FLP sites from the framework represents a groundbreaking innovation that expands the catalytic potential of existing materials. For catalysts already employing FLP chemistry to dynamically generate products from substrates, a complete mechanistic interpretation requires a thorough examination of the surface electronic properties and the surrounding environment. The hydrogen spillover ability on the Ru-doped FLP surfaces improves conversion efficiency by suppressing hydrogen poisoning at metal sites. In situ H2-H2O conditions enable the production of organic chemicals with excellent activity and selectivity by creating new bifunctional sites via FLP chemistry. By highlighting the novel FLP systems featuring FLP induction and synergistic effects and the selection of advanced characterization techniques to elucidate reaction mechanisms, we hope that this Account will offer innovative strategies for designing and characterizing FLP chemistry in heterogeneous catalysts to the research community.

Structure-directing effect of terephthalate in bridging Zn(II)- and Cd(II)-based coordination polymers towards application in the detection of trace quantities of Pd2+ in aqueous media and their electrical conductivities

Energy crisis and environmental pollution are two central themes of contemporary research towards achieving sustainable development goals (SDGs). Material chemistry is the chief discipline that can resolve glitches in these areas through the appropriate design of chemical compounds with multifunctional properties. In this regard, two stable coordination polymers (CPs) were synthesised in this work using Zn(II) (3d10) and Cd(II) (d10) metal nodes with 1,4-benzenedicarboxylate (bdc2-) as the bridging ligand and monodentate pyridyl-N coordinated 9H-fluoren-2-yl-pyridin-4-ylmethylene-amine (flpy) as the fluorogenic partner. The structures of the polymers [Zn2(bdc)4(flpy)2]n (CP1) and [Cd(bdc)2(flpy)2(H2O)]n·(flpy) (CP2) were confirmed via single-crystal X-ray diffraction measurements. In CP1, the paddle-wheel coordination unit [Zn2(bdc)4] was propagated to constitute a 2D polymer, while in CP2, the capped octahedron motif CdN2O5 generated a 1D chain. Both CP1 and CP2 were strongly emissive, and the emission could be quenched selectively by Pd2+ in aqueous solutions in the presence of as many as twenty other metal ions. Pd(II) is the most toxic in its three oxidation states of 0, II, and IV, and the limit of detection of Pd2+(aq) was 79.1 nM (CP1) and 89.2 nM (CP2), which were much below the toxicity limit of Pd2+ recommended by WHO (the tolerance limit of Pd2+ in water is 3.97-46.98 μM). Based on the Tauc plots of the ITO/(CP1 or CP2)/Al thin films, the bandgaps were determined as 3.63 eV for CP1 (theoretical value = 3.28 eV) and 3.55 eV for CP2 (theoretical value = 3.21 eV). Moreover, the electrical conductivity values of the Schottky semiconducting devices fabricated using these polymers at ambient conditions were 1.285 × 10-4 (CP1) and 2.399 × 10-4 S m-1 (CP2). Therefore, the application of these two CPs can accomplish sustainability goals for future generations.

Spin-Frustrated Metal-Organic Frameworks

Metal-organic frameworks (MOFs) are a fascinating class of structured materials with diverse functionality originating from their distinctive physicochemical properties. This review focuses on the specific chemical design of geometrically frustrated MOFs along with the origin of the intriguing magnetic properties. We have discussed the arrangement of spin centres (metal and ligand) which are responsible for the unusual magnetic phenomena in MOFs. Both two-dimensional (2D) and three-dimensional (3D) MOFs with frustrated magnetism, their synthetic routes, and evaluation of magnetic properties are highlighted. Such spin-frustrated MOFs may find applications in the field of memory devices, transistors, sensors, and the development of unconventional superconductors.

Solid phase extraction-surface enhanced Raman spectroscopy (SPE-SERS) test of antibiotic residues in Milk based on au@ MIL-101 NPs

A SPE-SERS method was developed for the detection of several antibiotic residues in dairy products. Gold nanoparticles (Au NPs) encapsulated with an ultrathin Cr-MIL-101 shell (Au@Cr-MIL-101 NPs) have been synthesized, and the thickness of Cr-MIL-101 shell can be precisely controlled to 3 nm. As a superior solid phase extraction (SPE) adsorbent, Cr-MIL-101 acts as a shell layer to effectively enrich antibiotics within the localized surface plasmon resonance (LSPR) field of Au NPs, which enhances the SERS signal and eliminates background interference. The method can achieve highly sensitive and high-throughput detection for tetracycline hydrochloride, sulfapyridine and benzylpenicillin sodium in dairy products, and the detection limits (LOD) are as low as 2.237, 2.644 and 4.662 ppb respectively. The recoveries of antibiotic residues in spiked dairy products ranged from 72.31 % to 146.7 % with matrix effects (ME) of -15.13 % to 28.68 %. Thus, this method holds significant promise for rapid detection of antibiotics in milk.

Novel amino-functionalized MOF-based sensor for zinc ion detection in water and blood serum samples

Aquatic systems with low zinc levels can experience a significant decrease in carbon dioxide uptake and limited growth of phytoplankton species. In this study, we describe the use of a new fluorescent sensor based on NH2-MIL-53(Al), and modified with glutaraldehyde and sulfadoxine, for selectively detecting zinc ions in water and blood serum samples. Characterization of the synthesized material was performed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) surface area analysis, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), confirming successful functionalization and preservation of the MOF structure. The sensor's performance for Zn2+ detection was evaluated by spectrofluorometry, demonstrating a significant fluorescence enhancement upon Zn2+ binding due to the interaction between Zn2+ ions and the sulfonamide groups. With a detection limit as low as 3.14 × 10-2 ppm, the sensor demonstrates high selectivity for Zn2+ over other common metal ions. The sensor's response is rapid, stable, and reproducible, making it suitable for practical applications. Real sample analysis was conducted in tap water and blood serum samples, with the results compared to those obtained using ICP-OES and a colorimetric test with 5-bromo-PAPS. The comparison confirmed the high accuracy and reliability of the fluorescent sensor in detecting Zn2+ ions in complex matrices. NH2-MIL-53(Al) modified with glutaraldehyde and sulfadoxine shows potential as a selective fluorescent sensor for Zn2+ detection, making it a valuable tool for monitoring the environment and biology.

Functional flexible adsorbents and their potential utility

Physisorbents are poised to address global challenges such as CO2 capture, mitigation of water scarcity and energy-efficient commodity gas storage and separation. Rigid physisorbents, i.e. those adsorbents that retain their structures upon gas or vapour exposure, are well studied in this context. Conversely, cooperatively flexible physisorbents undergo long-range structural transformations stimulated by guest exposure. Discovered serendipitously, flexible adsorbents have generally been regarded as scientific curiosities, which has contributed to misconceptions about their potential utility. Recently, increased scientific interest and insight into the properties of flexible adsorbents has afforded materials whose performance suggests that flexible adsorbents can compete with rigid adsorbents for both storage and separation applications. With respect to gas storage, adsorbents that undergo guest-induced phase transformations between low and high porosity phases in the right pressure range can offer improved working capacity and heat management, as exemplified by studies on adsorbed natural gas storage. For gas and vapour separations, the very nature of flexible adsorbents means that they can undergo induced fit mechanisms of guest binding, i.e. the adsorbent can adapt to a specific adsorbate. Such flexible adsorbents have set several new benchmarks for certain hydrocarbon separations in terms of selectivity and separation performance. This Feature Article reviews progress made by us and others towards the crystal engineering (design and control) of flexible adsorbents and addresses several of the myths that have emerged since their initial discovery, particularly with respect to those performance parameters of relevance to natural gas storage, water harvesting and hydrocarbon gas/vapour separation.

ZIP-8/Ag-based size-selective SERS nanoplatform for ultrasensitive urea detection in milk samples: effects of analyte molecular dimensions on adsorption capacity and sensing performance

Being well-known as an excellent sorbent, metal-organic frameworks (MOFs) have been employed to intergrate with noble metal nanoparticles to fabricate active substrates for surface-enhance Raman spectroscopy (SERS) sensing applications. In this work, we employed three organic molecules with different molecular dimensions, including urea, methylene blue (MB) and Congo red (CR) for investigating SERS performance of a ZIP-8/Ag heterostructure. While every dimension of urea is smaller than the pore size of ZIP-8, MB and CR has one dimension larger than that of the pore size. The results show that only urea experienced large SERS enhancements on ZIP-8/Ag sensing platform. In contrast, MB and CR exhibited lower SERS intensity on ZIP-8/Ag than on pure Ag nanoparticle substrates. Adsorption capacities of those analyte were then calculated to confirm that urea could be adsorbed into ZIP-8/Ag at the best rate. The size-dependent mechanism of analyte adsorption and improving SERS signal was then confirmed using two other organic compounds: 4-nitrophenol (4-NP) and chloramphenicol (CAP). Thanks to the size-selective adsorption, small molecules such as urea and 4-NP can be effectively detected in the presence of large interfering molecules, which is useful for developing advanced SERS applications. The ZIP-8/Ag-based SERS sensor could detect urea at impressive concentrations as low as 1.48 × 10-10 M in standard solutions and 10-8 M in milk.

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.

Electrochemical sensing system based on coordination bond connected porphyrin-MOFs@MXenes hybrids for in situ and real-time monitoring of H2O2 released from cells

Herein, the coordination bond connected porphyrin-MOFs/MXenes composites has been prepared to construct an electrochemical sensing system for in situ and real-time monitoring of H2O2 released by cells. The composites were synthesized by introducing 4-mercaptopyridine and utilizing its binding interaction with titanium in Mxenes and iron in MOFs. This composite was then transferred to the surface of ITO to construct an electrochemical sensing system. The unique properties of Mxenes and porphyrin MOFs endowed the sensing system with excellent electrocatalytic activity, good electrical conductivity and desirable biocompatibility. The electrochemical detections of hydroquinone verified the superior electrochemical performances of the sensing system. The constructed system achieved sensitive electrochemical detection of H2O2 with a detection limit of 3.1 µM and a linear range of 10 µM to 3 mM. Furthermore, the excellent biocompatibility of the composites ensured HeLa cells growth and proliferation on its surface. Based on these favorable properties, the sensing system successfully achieved in-situ and real-time monitoring of H2O2 released by HeLa cells.

Microenvironment Matters: Copper-Carbon Composites Enable a Highly Efficient Carbon Dioxide Reduction Reaction to C2 Products

Copper is the catalyst widely used to produce multicarbon products for the carbon dioxide reduction reaction (CO2RR). The surrounding microenvironment of copper plays a crucial role in determining its catalytic activity and selectivity. In this study, we compare three copper electrocatalysts with different microenvironments: pure metallic copper, a copper metal-organic framework (MOF), and a MOF-derived copper-carbon composite. Operando X-ray absorption spectroscopy, transmission electron microscopy, and Raman spectroscopy reveal that copper in the copper-carbon composite remains in a metallic state, encapsulated by a carbon matrix. The composite catalyst achieves a Faradaic efficiency of 75.6% for C2 products, including ethylene and ethanol, at a current density of 500 mA cm-2, with a C2 current density of 377.9 mA cm-2. This performance suppresses pure metallic copper, which reaches an optimal Faradaic efficiency of 64.5% for C2 products at a current density of 300 mA cm-2, with a C2 current density of 193.5 mA cm-2. The copper-carbon composite also significantly overperforms the copper-MOF catalyst, which shows an optimal Faradaic efficiency of 52.0% for C2 products at a current density of 400 mA cm-2, with a C2 current density of 208.0 mA cm-2. These findings highlight the importance of the microenvironment near active copper sites in determining CO2RR efficiency. We hope that our results provide valuable insights for advancing catalyst design in carbon dioxide reduction, contributing to reduced carbon emissions and improved environmental sustainability.

Preparation of a 6FDA-DAM/ODA Mixed Matrix Membrane Doped with MOFs and Its Application in Gas Separation

Mixed matrix membranes (MMMs) can significantly improve gas separation performance, but the type and state of the filler in the membrane matrix are key indicators for the development of MMMs. Therefore, in this work, 6FDA-DAM/ODA (1:1), metal-organic frameworks (MOFs) with different particle sizes (UiO-66 and UiO-66-NH2) were synthesized, and then MOFs were doped into 6FDA-DAM/ODA to prepare MMMs. The effects of the dopant materials and their particle sizes on the gas separation performance of the membranes were investigated by testing the permeability of the MMMs to H2, CO2, CH4, and N2. When the dopant material was UIO-66, the permeability and selectivity of MMMs for each gas were significantly improved compared with that of the original membrane; when the dopant material was 300 nm UIO-66-NH2 with a loading of 10 wt %, the permeability performance and the CO2/CH4 selectivity increased from 44.1 to 57.2 compared with that of the original membrane. The permeation performance for CO2, N2, and H2 and the selectivity for CO2/N2, H2/N2, and H2/CH4 were also significantly improved. In terms of comprehensive separation performance, doping 300 nm UiO-66-NH2 was better than doping 70 and 400 nm UiO-66-NH2 and also showed excellent performance in 50:50 (vol/vol) CO2/CH4 binary mixed gas separation. This work provides an idea for the fabrication of MMMs for high-performance gas separation.

Exploring advanced nanostructures and functional materials for efficient hydrogen storage: a theoretical investigation on mechanisms, adsorption process, and future directions

Hydrogen is a promising candidate for renewable energy storage and transportation due to its high energy density and zero carbon emissions. Its practical applications face challenges related to safe, efficient storage and release systems. This review article investigates advanced nanostructured materials for hydrogen storage, including metal acetylide and cyanide complexes, B,N-doped γ-graphyne nanotubes (γ-GNT), lithium-phosphide double helices, and Ni-decorated carbon-based clusters. Density Functional Theory (DFT) based computations are used to analyze binding energies, thermodynamic stability, and adsorption mechanisms. Ni-decorated C12N12 nanoclusters demonstrate enhanced storage capacities, binding up to eight H2 molecules with a favorable N-(μ-Ni)-N configuration. Lithium-phosphide double helices show potential for 9.6 wt% hydrogen storage within a stable, semiconducting framework. Functionalization of γ-GNT with OLi2 at boron-doped sites significantly enhances storage potential, achieving optimal hydrogen binding energies for practical applications. Additionally, metal acetylide and cyanide complexes, stabilized by noble gas insertion, display thermodynamically favorable hydrogen adsorption. These results highlight the potential of these functionalized nanostructures for achieving high-capacity, reversible hydrogen storage. The nanostructures in this study, such as γ-graphyne nanotubes (γ-GNT), lithium-phosphide double helices, metal acetylide and cyanide complexes, and Ni-decorated carbon-based clusters, are selected based on their ability to exhibit complementary hydrogen adsorption mechanisms, including physisorption and chemisorption. γ-GNT offers high surface area and tunable electronic properties, ideal for physisorption enhanced by heteroatom doping. Lithium-phosphide double helices facilitate Kubas-like chemisorption through unsaturated lithium centers. Metal acetylide and cyanide complexes stabilize hydrogen adsorption via charge transfer and conjugated frameworks, while Ni-decorated clusters combine polarization-induced physisorption. These materials represent a strategic approach to addressing the challenges of hydrogen storage through diverse and synergistic mechanisms. The review also addresses challenges and outlines future directions to advance hydrogen's role as a sustainable fuel.

Recent innovations in in situ strategies to prepare metal-organic framework-based mixed matrix membranes

Mixed matrix membranes (MMMs) composed of metal-organic frameworks (MOFs) and polymer matrixes have garnered significant attention due to their potential to overcome the permeability-selectivity trade-off inherent in polymeric membranes. Nevertheless, the application and industrial production of MOF-based MMMs have been hindered by issues such as poor interfacial compatibility and cumbersome fabrication processes. Recently, in situ strategies have emerged as promising approaches for fabricating MOF-based MMMs, offering enhanced interfacial compatibility between MOF fillers and polymers, as well as a simplified construction process. Furthermore, these strategies enable the creation of cross-linked MMMs with significantly improved interfacial compatibility and mechanical properties, which are unattainable through traditional physical mixing methods. This feature article summarizes recent advancements in the in situ preparation of MOF-based MMMs, encompassing in situ MOF growth, in situ polymerization of polymer matrixes, combined in situ methods, and in situ post-treatment. Our contributions to the field of in situ strategies include the innovative design of efficient spray technology and the formation of asymmetric MMMs. These developments pave the way for the realization of high-performance MOF-based MMMs suitable for industrial applications.

Unlocking a radioactive pertechnetate (TcO4 -) treatment process with functionalized metal-organic frameworks (MOFs)

Technetium-99 (99Tc), a troublesome radioisotope prevalent in nuclear liquid waste, poses significant environmental and human health hazards due to its long half-life, high fission yield, and fast environmental mobility. The successful mitigation of 99Tc is imperative for nuclear waste management; however, it continues to present a significant obstacle. In this comprehensive review, we explore the state-of-the-art developments in separating TcO4 - ions using functionalized metal-organic framework (MOF) materials, spanning from 2010 to the present. We delve into the intricate separation mechanisms of TcO4 - ions, shedding light on advanced research avenues in this field. Furthermore, we aim to provide a comprehensive understanding of the underlying receptor chemistry that is necessary for the specific targeting of pertechnetate anion-based materials. This will provide valuable insights into the molecular characteristics that are crucial for the separation of TcO4 - ions from solutions containing nuclear waste. The review outlines perspectives and conclusions that pave a promising path for the comprehensive investigation of materials poised to revolutionize TcO4 - separation. Finally, we provide forward-looking recommendations for future research directions, opportunities, and associated challenges, to encourage more researchers to leverage TcO4 - selective materials for better management of environmental pollution.

A Lewis basic site rich metal-organic framework featuring a hydrogen-bonded acetylene nano-trap for the efficient separation of C2H2/CO2

The physical separation of C2H2 from CO2 on metal-organic frameworks (MOFs) has received a substantial amount of research interest due to its advantages of simplicity, security, and energy efficiency. However, the exploitation of ideal MOF adsorbents for C2H2/CO2 separation remains a challenging task due to their similar physical properties and molecular sizes. Herein, we report a unique C2H2 nano-trap constructed using accessible oxygen and nitrogen sites, which exhibits energetic favorability toward C2H2 molecules. This material exhibits a good acetylene capacity of 55.31 cm3 g-1 and high C2H2/CO2 selectivity of 7.0 under ambient conditions. We have combined in situ IR spectroscopy and in-depth theoretical calculations to unravel the synergistic interactions driven by the high density of accessible oxygen and nitrogen sites. Furthermore, dynamic breakthrough experiments confirmed the capability of TUTJ-201Ni for the separation of binary C2H2/CO2 mixtures. This study on Ni-based MOFs will enrich Lewis basic site rich MOFs for gas adsorption and separation applications.

Unraveling metal effects on CO2 uptake in pyrene-based metal-organic frameworks

Pyrene-based metal-organic frameworks (MOFs) have tremendous potential for various applications. With infinite structural possibilities, the MOF community often relies on simulations to identify the most promising candidates for given applications. Among thousands of reported structures, many exhibit limited reproducibility - in either synthesis, performance, or both - owing to the sensitivity of synthetic conditions. Geometric distortions that may arise in the functional groups of pyrene-based ligands during synthesis and/or activation cannot easily be predicted. This sometimes leads to discrepancies between in silico and experimental results. Here, we investigate a series of pyrene-based MOFs for carbon capture. These structures share the same ligand (1,3,6,8-tetrakis(p-benzoic acid)pyrene (TBAPy)) but have different metals (M-TBAPy, M = Al, Ga, In, and Sc). The ligands stack parallel in their orthorhombic crystal structure, creating a promising binding site for CO2. As predicted, the metal is shown to affect the pyrene stacking distance and, therefore, the CO2 uptake. Here, we investigate the metal's intrinsic effects on the MOFs' crystal structure. Crystallographic analysis shows the emergence of additional phases, which thus impacts the overall adsorption characteristics of the MOFs. Considering these additional phases improves the prediction of adsorption isotherms, enhancing our understanding of pyrene-based MOFs for carbon capture.

In Situ Crystallization of CsPbBr3 Nanocrystals within a Melt-Quenched Glassy Coordination Polymer

Lead halide perovskite nanocrystal materials such as CsPbX3 (X = Cl, Br, and I) have triggered an intense research upsurge due to their excellent scintillation performance. Herein, an in situ crystallization strategy is developed to grow CsPbBr3 nanocrystals (NCs) within a low-melting-point (280 °C) coordination polymer (CP) glass. The viscosity of coordination glass is reduced through a low-temperature (e.g., 50 °C) thermal treatment, enabling the short-distance migration of uniformly dispersed ions (Cs+, Pb2+, and Br-) to achieve in situ crystallization of CsPbBr3 NCs. Benefiting from the high transmittance (80% within the 500-800 nm range) and outstanding scintillation performance, the prepared CsPbBr3@ZnBr2(bIm+DMSO)2 (bIm = benzimidazole, DMSO = dimethyl sulfoxide) transparent luminescence glass exhibits an excellent X-ray imaging resolution of up to 25 lp/mm, outperforming many perovskite glass and crystalline scintillators. This work would provide an idea for the development of high-resolution scintillation screens that can be prepared at low temperatures.

Single-Atom Pt Loaded on MOF-Derived Porous TiO2 with Maxim-Ized Pt Atom Utilization for Selective Hydrogenation of Halonitro-benzene

The location control of single atoms relative to supports is challenging for single-atom catalysts, leading to a large proportion of inaccessible single atoms buried under supports. Herein, a "sequential thermal transition" strategy is developed to afford single-atom Pt preferentially dispersed on the outer surface of TiO2. Specifically, a Ti-MOF confining Pt nanoparticles is converted to PtNPs and TiO2 composite coated by carbon (PtNPs&TiO2@C-800) at 800 °C in N2. Subsequent thermal-driven atomization of PtNPs at 600 °C in air produce single-atom Pt decorated TiO2 (Pt1/TiO2-600). The resulting Pt1/TiO2-600 exhibits superior p-chloroaniline (p-CAN) selectivity (99 %) to PtNPs/TiO2-400 (45 %) and much better activity than Pt1@TiO2-600 with randomly dispersed Pt1 both outside and inside TiO2 in the hydrogenation of p-chloronitrobenzene (p-CNB). Mechanism investigations reveal that Pt1/TiO2-600 achieves 100 % accessibility of Pt1 and preferably adsorbs the -NO2 group of p-CNB while weakly adsorbs -Cl group of p-CNB and p-CAN, promoting catalytic activity and selectivity.

Self-Healing 2D Anion-Organic Frameworks for Low-Temperature Water Release

Molecular frameworks have recently shown a great potential in atmospheric water harvesting, in which the water release at low temperatures is challenging. Anion-organic frameworks based on anion-coordination chemistry are presented herein to meet this challenge. These frameworks are prepared as tubular single crystals in pure water from the in situ protonation and crystallization of pyridine-terminated triphenylamine derivatives with hydrochloric or hydrobromic acid. They possess a 2D honeycombed porous structure and carry halogen anions confined within 1D hexagonal nanochannels with a modular size of 1.7-2.3 nm. They exhibit a high water uptake of up to 0.87 g g-1 and a water release onset temperature as low as -90 °C. The water uptake and release induce significant changes in the crystal morphology and absorption and emission properties of these framework crystals, providing a visual indication of their hydration states over a wide temperature range. The kinetics of dehydration at subglacial temperatures is successfully determined by emission spectral shifts. These framework crystals show a high water-stability and can be used for repeated water capture and release thanks to a rapid and robust self-healing capability. This discovery opens opportunities for the design and synthesis of flexible and self-healing frameworks for porosity-related applications.

Ethane Triggered Gate-Opening in a Flexible-Robust Metal-Organic Framework for Ultra-High Purity Ethylene Purification

Priority recognition separation of inert and larger ethane molecules from high-concentration ethylene mixtures instead of the traditional thermodynamic or size sieving strategy is a fundamental challenge. Herein, we report ethane triggered gate-opening in the flexible-robust metal-organic framework Zn(ad)(min), the 3-methylisonicotinic acid ligand can spin as a flexible gate when adsorbing the cross-section well-matched ethane molecule, achieving an unprecedented ethane adsorption capacity (62.6 cm3 g-1) and ethane/ethylene uptake ratio (3.34) under low-pressure region (0.1 bar and 298 K). The ethane-induced structural transition behavior has been uncovered by a collaboration of single-crystal X-ray diffraction, in situ variable pressure X-ray diffraction and theoretical calculations, elucidating the synergetic mechanism of cross-section matching and multiple supramolecular interactions within the tailor-made pore channels. Dynamic breakthrough experiments have revealed the outstanding separation performance of Zn(ad)(min) during the production of ultra-high purity ethylene (>99.995 %) with a productivity of up to 39.2 L/kg under ambient conditions.

Semiconductive Coordination Polymer with Multi-Channel Charge Transfer for High-Performance Direct X-ray Detection

Coordination polymers (CPs) are promising for direct X-ray detection and imaging owing to higher designability and outstanding stability, however, it remains a challenge to achieve highly X-ray detection performance, particularly both high sensitivity and low detection limit at the same operating voltage. Herein, we construct a new conjugated CP {[Co(BPTTz)(DIPA)] ⋅ DMA}n (1, BPTTz=2,5-bis(pyridine-4-yl)thiazolo[5,4-d]thiazole, H2DIPA=2,5-diiodoterephthalic acid, DMA=N, N'-dimethylacetamide), with multi-channel charge transfer by regulating the linker mediated electronic-state, which reduces carrier losses resulting from recombination or quenching, enhances the efficiency of charge separation and transfer, thus further optimizes X-ray detection performance. The semiconductor prepared based on this strategy achieves record values including the highest mobility-lifetime product (μτ, 8.05×10-3 cm2 V-1) and the lowest detectable X-ray dose rate (128 nGyair S-1, 35 V) among CP-based direct radiation detectors, as well as a high sensitivity (172 μC Gyair -1 cm-2, 35 V) at the same operating voltage. This detector shows excellent long-time air stability under ambient conditions for over three months and operational stability. These findings demonstrate a rational structural design method to enhance the photoelectronic efficiency and stability of semiconductive CPs.

Drug Delivery Systems Based on Metal-Organic Frameworks for Tumor Immunotherapy

Metal-organic frameworks (MOFs) are a class of inorganic-organic hybrid nanoparticles formed by the coordination of metal ions/clusters and organic ligands. Due to their high porosities, large surface areas, adjustable structures, and responsiveness to light/sound, etc., MOFs have shown great clinical potential in the field of tumor therapy. Tumor immunotherapy exerts antitumor effects through reshaping tumor immune microenvironment, showing significant preclinical and clinical advantages. Based on the mechanisms of immunity activation, the tumor immunotherapy agents can be divided into chemotherapeutic agents, immunomodulators, enzymes, tumor vaccines and oligonucleotide drugs, etc. Herein, we review the MOFs-based drug delivery systems for tumor immunotherapy. The classification of MOFs, followed by their antitumor immunity activation mechanisms, are first introduced. Drug delivery systems based on MOFs with different immunotherapy agents are also summarized, especially the synergetic immunity activation mechanisms triggered by MOFs and their loadings. Furthermore, the merits and drawbacks of MOFs and the potential strategies for MOFs to promote their clinical applications are discussed.

Homochiral BINOL-Based Metal-Organic Frameworks for Luminescence Sensing of Hydrobenzoin Enantiomers

Luminescent chiral metal-organic frameworks (CMOFs) are promising candidates for the enantioselective sensing of important chiral molecules. Herein, we report the synthesis and characterization of Zn and Cd CMOFs based on 1,1'-bi-2-naphthol (BINOL)-derived 3,3',6,6'-tetra(benzoic acids), H4L-OEt and H4L-OH. Four CMOFs, Zn-L-OEt, Zn-L-OH, Cd-L-OEt, and Cd-L-OH, based on these ligands were crystallographically characterized. Zinc cations form 8-connected (8-c) penta-metallic secondary building units (SBUs), while cadmium cations form 4-c trimetallic SBUs. These SBUs are linked by 4-c L-OEt and L-OH ligands to form noninterpenetrated 4, 8-c 4,8T41 zinc CMOFs (Zn-L-OEt and Zn-L-OH) and 2-fold interpenetrated 4-c diamondoid (dia) cadmium CMOFs (Cd-L-OEt and Cd-L-OH), respectively. At a ligand concentration of 24 μM, H4L-OEt and H4L-OH showed negligible luminescent quenching by RR- and SS-hydrobenzoin (HB) enantiomers with Stern-Völmer constants of 29-89 M-1. In contrast, CMOFs displayed efficient quenching by HB enantiomers with Stern-Völmer constants of 583-1200 M-1, due to significant HB preconcentration in CMOF channels via favorable host-guest interactions between CMOF frameworks and HB molecules. The CMOFs demonstrated luminescence quenching selectivity for RR-HB over SS-HB, with Zn-L-OEt exhibiting the highest quenching ratio (Ksv(RR)/Ksv(SS)) of 1.624. This work highlights the potential of CMOFs in enantioselective sensing applications.

Enhancing the Chemical Stability of P12L24 Cage: Transformation of the Chemically Labile Imine Cage into a Robust Carbamate Cage

Herein, we report enhancement in chemical stability of the imine-based porphyrinic cage P12L24 by converting it into a robust carbamate porphyrinic cage, c-P12L24, through a two-step post-synthetic modification process. First, the imine bonds in P12L24 were reduced to form an amine-based cage, r-P12L24, followed by carbamation using N,N'-carbonyldiimidazole (CDI) to yield c-P12L24. The resulting carbamate cage exhibits high stability under acidic and basic conditions (pH 1-13) and in the presence of moisture. 1H NMR, DOSY NMR, and DFT calculations revealed that reducing the imine bonds to amine increases the framework's flexibility, causing partial structural collapse, whereas the carbamate formation restores structural rigidity. The insertion of a 4.0 nm molecular ruler into the cavity of zinc-metallated c-P12L24 via metal-ligand coordination further confirmed restoration of the cavity size and geometry of the original cage. This enhancement of chemical stability through carbamate formation can pave the way to a wide range of potential applications for the gigantic porphyrinic cage.

Growth of the metal-organic framework ZIF-67 on cellulosic substrates for triboelectric nanogenerators

Metal-organic frameworks (MOFs) are porous crystalline materials with a metal ion coordinated to a ligand molecule. Recently, MOFs are being explored extensively for energy harvesting via triboelectrification. However, the majority of MOFs are brittle and hard to grow, thus leading to poor device stability and flexibility. Herein, the growth of ZIF-67 MOF is achieved on a cellulosic filter paper (CFP) and cotton fabric (CF) separately to use as the active layer in a TENG. The grown ZIF-67 MOFs were used for the fabrication of CFP-TENG and CF-TENG in vertical contact separation mode. The CF-TENG device exhibited a high durability with no significant change in the electrical output for a period of 14 000 s. Additionally, the device generated a maximum electrical output of 60 V and 3 μA with an output power density of 5 mW m-2 at a load resistance of 800 MΩ. The robustness of the MOF grown on cotton fabric was demonstrated by fabricating a contact separation and rotating TENG device. The rotating TENG device produced an output voltage of ∼100 V and current of 3.5 μA, thus confirming the strong adherence of MOFs on the fabric. The CF-TENG was demonstrated for powering electronics via flexible circuits and for biomechanical energy harvesting by utilising finger tapping, hand tapping, jogging and running movements.

Comprehensive DFT investigation of small-molecule adsorption on the paradigm M-MOF-74 family of metal-organic frameworks

The capture of toxic chemicals such as NH3, H2S, NO2 and SO2 is essential due to the tremendous threats they pose to human health and the environment. The M-MOF-74 family of metal-organic frameworks has recently gained attention as a promising category of sorbent materials for the capture of toxic chemicals; however, no clear and comprehensive relationships have been established between the capability of the M-MOF-74 to capture all target toxic chemicals and their properties such as the nature and magnetic state of the metal sites. Density-functional theory (DFT) is employed to investigate the binding energy of target molecules on M-MOF-74 with different metals including Mg, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn. The Hubbard U correction is employed to properly treat d electrons of transition metals and its effect explored on the bandgap of M-MOF-74. The magnetic properties of M-MOF-74 are investigated in detail along with their impact on the target molecule adsorption. Our calculations with DFT+U lead to good agreement with available experimentally determined bandgaps and structural properties. M-MOF-74 (M = Ti, V, Cr, Mn, Fe, Co and Cu) exhibit antiferromagnetic behavior, while ferromagnetic behavior prevails for Ni-MOF-74. Not surprisingly, the coordinatively unsaturated metals (M = Mg, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) are the most likely sites for chemical adsorption of the target adsorbates, and V-MOF-74 and Ti-MOF-74 predicted to be efficient adsorbents for the target molecules, which can be rationalized on the basis of the metal d-band features. The spin configuration of transition metals in M-MOF-74 is found to have a negligible effect on adsorbate binding energies, which suggests that common DFT calculations without careful consideration of the material magnetic states can indeed be used to rapidly screen binding energies of adsorbates on such MOFs, with some notable exceptions; for instance, V-MOF-74 shows potential for magnetic sensing of NO2. This study provides further insight into the role of different unsaturated metals and their magnetic state for the removal of target toxic molecules by metal-organic frameworks.

Observation of O2 Molecules Inserting into Fe-H Bonds in a Ferrous Metal-Organic Framework

Exploring the interactions between oxygen molecules and metal sites has been a significant topic. Most previous studies concentrated on enzyme-mimicking metal sites interacting with O2 to form M-OO species, leaving the development of new types of O2-activating metal sites and novel adsorption mechanisms largely overlooked. In this study, we reported an Fe(II)-doped metal-organic framework (MOF) [Fe3Zn2H4(bibtz)3] (MAF-203, H2bibtz = 1H,1'H-5,5'-bibenzo[d][1,2,3]triazole), featuring an unprecedented tetrahedral Fe(II)HN3 site. This MOF exhibits selective adsorption behavior for O2 from air, achieving an O2/N2 separation selectivity of up to 67.1. Breakthrough experiments confirmed that MAF-203 can effectively capture O2 from the air even under a high relative humidity of 60%. X-ray absorption spectroscopy, in situ diffuse reflectance infrared Fourier transform spectra, and ab initio molecular dynamics simulations were utilized to monitor the O2 loading process on the Fe(II)HN3 site. Interestingly, O2 molecules could insert into the Fe-H bonds of the tetrahedral FeIIHN3 sites, forming FeIII-OOH species (instead of the commonly observed Fe-OO species) with an ultrahigh adsorption enthalpy of -99.2 kJ mol-1. Consequently, the O2 capture behavior of MAF-203 enables efficient electrochemical 2e- oxygen reduction for the production of H2O2 with air as the feedstock. Specifically, in a solid-state electrolyte electrolyzer without any liquid electrolyte, MAF-203 achieved selective O2 capture and continuous production of medical-grade H2O2 (3.2 wt %) solution without salts for 70 h, with performance comparable to that under pure O2 conditions. The O2 adsorption and activation mechanisms inaugurate a fresh chapter in grasping the interaction between O2 molecules and metal sites.

Copper catalyzed selective methane oxidation to acetic acid using O2

The direct transformation of methane into C2 oxygenates such as acetic acid selectively using molecular oxygen (O2) is a significant challenge due to the chemical inertness of methane, the difficulty of methane C-H bond activation/C-C bond coupling and the thermodynamically favored over-oxidation. In this study, we have successfully developed a porous aluminium metal-organic framework (MOF)-supported single-site mono-copper(ii) hydroxyl catalyst [MIL-53(Al)-Cu(OH)], which is efficient in directly oxidizing methane to acetic acid in water at 175 °C with a remarkable selectivity using only O2. This heterogeneous catalyst achieved an exceptional acetic acid productivity of 11 796 mmolCH3CO2H molCu -1 h-1 in 9.3% methane conversion with 95% selectivity in the liquid phase and can be reused at least 6 times. Our experiments, along with computational studies and spectroscopic analyses, suggest a catalytic cycle involving the formation of a methyl radical (˙CH3). The confinement of Cu-active sites within the porous MIL-53(Al) MOF facilitates C-C bond coupling, resulting in the efficient formation of acetic acid with excellent selectivity due to the internal mass transfer limitations. This work advances the development of efficient and chemoselective earth-abundant metal catalysts using MOFs for the direct transformation of methane into value-added products under mild and eco-friendly conditions.

Application and progress of 3D printed biomaterials in osteoporosis

Osteoporosis results from a disruption in skeletal homeostasis caused by an imbalance between bone resorption and bone formation. Conventional treatments, such as pharmaceutical drugs and hormone replacement therapy, often yield suboptimal results and are frequently associated with side effects. Recently, biomaterial-based approaches have gained attention as promising alternatives for managing osteoporosis. This review summarizes the current advancements in 3D-printed biomaterials designed for osteoporosis treatment. The benefits of biomaterial-based approaches compared to traditional systemic drug therapies are discussed. These 3D-printed materials can be broadly categorized based on their functionalities, including promoting osteogenesis, reducing inflammation, exhibiting antioxidant properties, and inhibiting osteoclast activity. 3D printing has the advantages of speed, precision, personalization, etc. It is able to satisfy the requirements of irregular geometry, differentiated composition, and multilayered structure of articular osteochondral scaffolds with boundary layer structure. The limitations of existing biomaterials are critically analyzed and future directions for biomaterial-based therapies are considered.

Photosensitizable ZIF-8 BioMOF for Stimuli-Responsive Antimicrobial Phototherapy

Resistant pathogens are increasingly posing a heightened risk to healthcare systems, leading to a growing concern due to the lack of effective antimicrobial treatments. This has prompted the adoption of antimicrobial photodynamic therapy (aPDT), which eradicates microorganisms by generating reactive oxygen species (ROS) through the utilization of a photosensitizer, photons, and molecular oxygen. However, a challenge arises from the inherent characteristics of photosensitizers, including photobleaching, aggregation, and self-quenching. Consequently, a strategy has been devised to adsorb or bind photosensitizers to diverse carriers to facilitate their delivery. Notably, metal-organic frameworks (MOFs) have emerged as a promising means of transporting photosensitizers, even though achieving uniform particle sizes through room-temperature synthesis remains a complex task. In this work, we have tackled the issue of heterogeneous particle size distribution in MOFs, achieving a particle size of 150 ± 50 nm. Subsequently, we harnessed Zeolite Imidazolate Framework 8 (ZIF-8), an excellent subclass of biocompatible MOF, to effectively load two distinct categories of photosensitizers, namely, Rose Bengal (RB) and porphyrin, using a simple, straightforward, and single-step process. Our findings indicate that the prepared RB@ZIF-8 complex generates a more substantial amount of reactive singlet oxygen species when subjected to photoirradiation (using green light-emitting diode (LED)) at low concentrations, in comparison with porphyrin@ZIF-8, as demonstrated in in vitro experiments. Additionally, we investigated the pH-responsive behavior of the complex to ascertain its implications under biological conditions. Correspondingly, the RB@ZIF-8 complex exhibited a more favorable IC50 value against Escherichia coli compared to bare photosensitizers, ZIF-8 alone, and other photosensitizer-loaded ZIF-8 complexes. This underscores the potential of BioMOF as a promising strategy for combatting multidrug-resistant bacteria across a spectrum of infection scenarios, complemented by its responsiveness to stimuli.

Mixed-valence metal-organic frameworks: concepts, opportunities, and prospects

Owing to increasing global demand for the development of multifunctional advanced materials with various practical applications, great attention has been paid to metal-organic frameworks due to their unique properties, such as structural, chemical, and functional diversity. Several strategies have been developed to promote the applicability of these materials in practical fields. The induction of mixed-valency is a promising strategy, contributing to exceptional features in these porous materials such as enhanced charge delocalization, conductivity, magnetism, etc. The current review provides a detailed study of mixed-valence MOFs, including their fundamental properties, synthesis challenges, and characterization methods. The outstanding applicability of these materials in diverse fields such as energy storage, catalysis, sensing, gas sorption, separation, etc. is also discussed, providing a roadmap for future design strategies to exploit mixed valency in advanced materials. Interestingly, mixed-valence MOFs have demonstrated fascinating features in practical fields compared to their homo-valence MOFs, resulting from an enhanced synergy between mixed-valence states within the framework.