Hierarchically Porous MOFs Synthesized by Soft-Template Strategies

Ordered mesoporous metal-organic frameworks directed by amphiphilic block polymer as soft-template in N,N-dimethylformamide media

Ordered mesoporous Metal-Organic Frameworks (mesoMOFs), integrating mesopores and micropores, address mass transfer limitations characteristic of microporous materials, thus broadening their application spectrum. However, the synthesis of mesoMOFs has been predominantly achievable in aqueous media, rather than in organic solvents, which are more conducive to the growth and stabilization of MOFs. This is primarily attributed to the challenge in forming stable and uniform micelles from block copolymers within organic systems. In this work, mesoMOFs are synthesized within N,N-dimethylformamide (DMF) media for the first time, via a micellar microphase separation method facilitating by introducing trace water into the organic solvent DMF. These mesoMOFs, featuring non-exposed spherical mesopores and inherent microporosity, demonstrate significantly enhanced performance in the accumulation of reactants, and such characteristics render these materials ideal nanoreactors, endowing them with superior adsorption and degradation capabilities. The adsorptive and degradation removal of tetracycline (TC) by mMIL-101 reached 93.7%, with its efficiency in both adsorption and degradation of TC being significantly higher than that of traditional MIL-101. This synthetic approach expands the scope of mesoMOFs preparation in organic solvents, providing insights for designing a new generation of mesoMOFs with diverse compositions and structures, promising applications across various fields and advancing MOF-based technologies.

Hierarchical Engineering of Single-Crystalline Mesoporous Metal-Organic Frameworks with Hollow Structures

Although the superiority of hierarchical structure has driven extensive demand for applications, establishing hierarchy in a long-range-ordered single crystal remains a formidable challenge due to the inherent competition and contradiction between single crystallinity and controllable hierarchical structure. Herein, we demonstrate a growth and dissociation kinetics cooperative strategy for synthesizing a family of hollow single-crystalline mesoporous metal-organic frameworks (meso-MOFs) with hierarchical structures. The approach employs a dual-template method, integrating both hard and soft templates. By adjusting the HCl/CH3COOH ratio, the reaction system's pH can be tuned to regulate the dissociation kinetics of the acid-sensitive seeds serving as hard templates for the formation of hollow structure, while simultaneously modifying the concentration of the dual acids to control the growth kinetics of meso-MOF shells. The competition between maintaining a single crystallinity and achieving a well-defined hierarchical structure can be effectively balanced. Driven by the two interfacial kinetics, we successfully obtained the octahedral meso-MOF nanoparticles that not only exhibit a well-defined hollow structure with precisely controllable hollow size (∼81-1120 nm) and tunable wall thickness (∼28.6-61.3 nm) but also retain their single-crystal integrity. Specifically, the dissociation kinetics of seeds governed the formation of hollow structures, while the growth kinetics of single-crystalline meso-MOF shells ensured uniform coverage and structural integrity. Based on this strategy, we further developed a series of novel hollow meso-MOFs with hierarchical nanostructures, including hollow open-capsule meso-MOFs, 2D hollow meso-MOFs, hollow interlayer-structured meso-MOFs, macro-meso-micro trimodal porous MOFs, and so on.

Selective Design of Mesoporous Bi2Se3 Films with Orthorhombic and Rhombohedral Crystals

Materials with the same chemical composition can exhibit distinct properties depending on their crystal phases. Here, the synthesis of two types of mesoporous Bi2Se3 films at different reduction potentials is reported and their application in electrochemical glucose sensing. Mesoporous Bi2Se3 is synthesized by incorporating block copolymer micelle assemblies into the deposition solution and applying a reduction potential. To characterize the crystal phases accurately, Bi2Se3 films are heat-treated at 200 °C for 1 h in a nitrogen atmosphere. The results reveal that the Bi2Se3 films synthesized under different conditions exhibit clearly distinct phases: rhombohedral (R-Bi2Se3) and orthorhombic (O-Bi2Se3). The R-Bi2Se3-8 nm, featuring 8 nm pores and synthesized at a more negative reduction potential, outperforms its nonporous counterpart, achieving a glucose sensing sensitivity of 0.143 µA cm-2 µM-1 and a detection limit of 6.2 µM at pH 7.4 in 0.1 M phosphate-buffered saline solution. In contrast, the O-Bi2Se3, prepared at a relatively positive potential, exhibits no glucose-sensing activity. The inactivity of O-Bi2Se3 for glucose oxidation is likely due to the energetically unfavorable intermediates, as predicted by density functional theory calculations. These findings underscore the critical role of crystal phase control in porous nanomaterials and pave the way for developing innovative porous systems.

Ordered Co-Assembly of Soft-in-Hard Hetero-Structured Pulse Guidance Ion-Accelerator for Dendrite-Free Aqueous Zinc-Ion Battery Anodes

Constructing a solid electrolyte interface (SEI) layer to suppress dendrite growth is an effective approach in Zn-based aqueous batteries. Traditional SEI layers are limited by their simple structure and composition, enabling only one functionality of either providing nucleation sites or facilitating desolvation. In this study, a pulse guidance ion-accelerator is constructed by kinetics-controlled co-assembly of zincophilic micelles and zincophobic metal-organic framework (MOF). The closely packed soft micelles, in conjunction with the hard MOF host particles, form a multi-tiered soft-in-hard hetero-structure that accelerates adsorption, pre-desolvation, and subsequent desolvation processes, facilitating the (002) crystal plane dendrite-free deposition. As a result, stable cycling over 1900 h (31 mV polarization) in symmetric cell and 5200 cycles in the Zn//Cu battery (99.8% coulombic efficiency) can be achieved. These findings will effectively promote the development of stable and long-cycling aqueous zinc-ion batteries.

Unlocking coordination sites of metal-organic frameworks for high-density and accessible copper nanoparticles toward electrochemical nitrate reduction to ammonia

Ordered pore engineering of metal-organic framework (MOF)-based catalysts by soft-template strategies can facilitate the mass transfer of reactants during heterogeneous electrocatalysis. Besides, the abundant open coordination sites generated by the removal of surfactants also open up a new avenue for incorporating active moieties within the framework; however, such studies are still limited. Herein, a mesoporous cerium-based MOF, MUiO-66(Ce), is synthesized by introducing a pluronic triblock copolymer as a template, where abundant open coordination sites are found to be present on the hexa-cerium nodes. By providing rich Ce-OH/Ce-OH2 sites, plenty of copper moieties are installed on the framework (denoted as Cu-MUiO-66(Ce)). After the in situ reduction process, a high density of copper nanoparticles is confined within MUiO-66(Ce), and Cu@MUiO-66(Ce) is thus obtained. With a high loading of active copper sites and efficient diffusion of reactants, the Cu@MUiO-66(Ce)-modified electrode can achieve an ammonia production rate of 1.875 mg h-1 mgcatalyst -1 and a faradaic efficiency of 88.7% for nitrate-to-ammonia reduction. Findings here shed light on the importance of pore engineering of MOF-based catalysts for unlocking open coordination sites and facilitating the mass transfer to enhance the electrocatalytic activity.

Construction of Hierarchically Porous Metal-Organic Frameworks via A Novel Metal Ion-Modulation Approach: A Complementary Approach to Linker-Modulation

Hierarchically porous metal-organic frameworks (HP-MOFs) always present novel and advanced performances in many applications. Herein, we demonstrated a novel mechanochemical metal modulation strategy to construct the HP-MOFs. The metal modulator bearing different coordination ability from the parent metal was incorporated into the parent metal precursor via ball milling. Then, by reacting with the ligand, the metal modulator interrupted the original metal-ligand coordination and created the defect-mesopores during the solid-state transformation process, resulting in HP-MOF. Using this approach, a series of HP-MOFs were constructed. Notably, unlike the linker modulation approach, the missing-linker defects are no longer the dominant defects in these prepared HP-MOFs. Beyond this, the metal modulators can be co-assembled into the HP-MOFs, functionalizing HP-MOFs with new metal active sites. Finally, the catalytic performances of prepared hierarchically porous ZIF-8-Pd was tested, it presented superior catalytic activities towards hydrogenation of unsaturated aldehydes.

A novel hierarchical porous ZIF-8 for effective removal of three non-steroidal anti-inflammatory drugs simultaneously from environment

Metal organic frameworks (MOFs) adsorbents have significant advantages to remove contaminates. While their microporous structure is not conducive to entry of larger molecules, making it difficult to simultaneously utilize the inner and outer surfaces of the pores to achieve higher adsorption capacity. In this work, the hexadecyltrimethylammonium bromide was employed as soft template to prepare a novel hierarchical porous ZIF-8 (HP-ZIF-8) in water. The result showed that the developed HP-ZIF-8 has both microporous (0.59 nm) and mesoporous structures (35.59 nm), which is 33 times larger than that of initial ZIF-8 (1.08 nm). Mesoporous HP-ZIF-8 enhances adsorption, enabling simultaneous capture of diclofenac sodium (DFS), flunixin meglumine (FM), and meloxicam (ME). The adsorption process for DFS, FM, and ME was agreement with the Langmuir model, and maximum adsorption capacities were 119.33, 162.87, and 40.45 mg g-1, respectively. Moreover, the mesopores effectively enhance mass transfer rate, and the adsorption equilibrium can be reached within 10 min. Mechanistic analysis revealed that DFS, FM, and ME adsorption onto HP-ZIF-8 was driven by hydrogen bonding, π-π stacking, electrostatic and metal coordination interactions, alongside mesoporous structure-induced physical adsorption. Furthermore, HP-ZIF-8 was successfully applied in the removal of these pharmaceutical compounds from five different real water samples and three food matrices, achieving recoveries between 84.54% and 106.59%, with relative standard deviations below 4.05%. This work provides a simple and feasible method to improve the adsorption performance of MOFs, making them efficiently adsorbing and removing pollutants from the environment.

Tailoring the Morphology of α-Cobalt Hydroxide Using Liquid/Liquid Interface and Its Application in Electrochemical Detection of Ascorbic Acid

The exertion of nanomaterials is subjugated by factors such as size, thickness, morphology, crystallinity, and composition, however, the ability to control these parameters, particularly the morphology, through conventional synthesis methods are challenging. Nevertheless, liquid/liquid interface-assisted methods have paved the way for more precise and controlled synthesis of nanomaterials. In this study, an n-butanol/water interface was used to synthesize α-cobalt hydroxide (CH) nanostructures, and the effects of solvent ratio and stirring rate on the properties of the product were examined. The transition from pure water to pure n-butanol alters the morphology from irregular nanoflakes to flower-like structures. A 1:1 solvent ratio produced nonaggregated flower structures with an increased active surface area and minimal charge transfer resistance. The agitation speed also affected the morphology; as the stirring speed increased from zero to 150 rpm, the morphology changed from aggregated needles to flower-like structures. The sample synthesized with a 1:1 solvent ratio and 50 rpm stirring speed (BW2) exhibited enhanced electrochemical activity, which was harnessed for electrochemical sensing with minimal multiwalled carbon nanotube (MWCNT) addition. The CH/MWCNT composite effectively detected ascorbic acid (AA) across a broad linear range of 1-200 μM with a detection limit of 0.0943 μM and provided accurate AA recovery in vitamin C tablets and artificial sweat. A flexible miniature sensor was also developed for AA detection, demonstrating the potential of liquid/liquid interfaces to modulate the morphology and hence the electrochemical properties of transition metal oxides for a wide range of applications.

The structuring of porous reticular materials for energy applications at industrial scales

Reticular synthesis constructs crystalline architectures by linking molecular building blocks with robust bonds. This process gave rise to reticular chemistry and permanently porous solids. Such precise control over pore shape, size and surface chemistry makes reticular materials versatile for gas storage, separation, catalysis, sensing, and healthcare applications. Despite their potential, the transition from laboratory to industrial applications remains largely limited. Among various factors contributing to this translational gap, the challenges associated with their formulation through structuring and densification for industrial compatibility are significant yet underexplored areas. Here, we focus on the shaping strategies for porous reticular materials, particularly metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), to facilitate their industrial application. We explore techniques that preserve functionality and ensure durability under rigorous industrial conditions. The discussion highlights various configurations - granules, monoliths, pellets, thin films, gels, foams, and glasses - structured to maintain the materials' intrinsic microscopic properties at a macroscopic level. We examine the foundational theory and principles behind these shapes and structures, employing both in situ and post-synthetic methods. Through case studies, we demonstrate the performance of these materials in real-world settings, offering a structuring blueprint to inform the selection of techniques and shapes for diverse applications. Ultimately, we argue that advancing structuring strategies for porous reticular materials is key to closing the gap between laboratory research and industrial utilization.

Light-Responsive Nanoemulsion-Guided Assembly of Honeycomb Hierarchically Macro/mesoporous Metal-Organic Framework Nanoarchitectures

Despite that soft template pathways are promising avenues for synthesizing hierarchically porous metal-organic framework (MOF) nanoparticles, smart-responsive-directed assembly strategies have been rarely extended to fabricate well-defined hierarchical macro/mesoporosities in MOF architectures. Herein, a novel light-responsive nanoemulsion-guided strategy is reported to prepare honeycomb hierarchically porous UiO-66 nanoparticles (UiO-66 HHPNPs) with macro/mesoporosities transition using poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (F127, PEO106PPO70PEO106) and azobenzene (Azo) as a light-responsive soft template. By facilely tuning the concentration of Azo and light irradiation (e.g., 365 nm ultraviolet light), the assembled UiO-66 HHPNPs varies from microporous architectures to macro/mesoporous dendritic architectures with an average pore size expanding from 14 to 135 nm. It is worth noting that the cis-trans configuration transformation of Azo under the irradiation of 475 nm blue light results in the shrunken micelles and thus rapid template removal from macro/mesoporous architectures of UiO-66 HHPNPs. Additionally, a light-responsive soft template can also alter the pore structures of other MOF nanoparticles (e.g., zirconium-based UiO-66). Importantly, the resultant macro/mesoporous UiO-66 HHPNPs reveal superior catalytic activity than the microporous UiO-66 HHPNPs in the 3,3',5,5'-tetramethylbenzidine catalytic reaction system. This newfangled light-induced template assembly technique paves an attractive way for the rational design of multimodal macro/mesoporous architectures and thus renders them broad applications.

Construction and Band Gap-Regulation of Ordered Macro-Microporous Single Crystals of an Amine-Linked Covalent Organic Framework

Heterogeneity engineering provides an effective route to manipulate the chemical and physical properties of covalent organic frameworks (COFs) but is still under development for their single-crystal form. Here, we report the strategy based on a combination of the template-assisted modulated synthesis with a one-pot crystallization-reduction method to directly construct ordered macro-microporous single crystals of an amine-linked three-dimensional (3D) COF (OM-COF-300-SR). In this strategy, the colloidal crystal-templating synthesis not only assists the formation of ordered macropores but also greatly facilitates the in situ conversion of linkages (from imine to amine) in the COF-300 single crystals. The as-synthesized OM-COF-300-SR120 exhibits a reversible symmetry change from a tetragonal I41/a to monoclinic I2/c space group after activation, which was not observed previously. On the other hand, this strategy allows for a flexible control over the degree of amination (from 0 to 100%, as determined by X-ray photoelectron spectroscopy (XPS) analysis) in COF-300 crystals to regulate their band gap (from 2.57 to 2.81 eV) for the optimization of photocatalytic activity. The high degree of amination and the embedded ordered macropores render OM-COF-300-SR120 with superior photocatalytic activity (with a reaction rate constant of 0.9572 min-1) to its nonmacroporous counterpart (NM-COF-300-SR120, 0.2303 min-1) for the degradation of rhodamine B. In addition, the significant contribution of ordered macropores to confront mass transfer resistance in COF single crystals was also confirmed by the much higher catalytic activity of Au/OM-COF-300-SR120 (with an activity parameter of 7.96 × 103 s-1 mol-1) as compared with Au/NM-COF-300-SR120 (1.43 × 103 s-1 mol-1) in the model reduction reaction of 4-nitrophenol by NaBH4.

Prussian blue nanocages as efficient radical scavengers and photothermal agents for reducing amyloid-beta induced neurotoxicity

The unusual accumulation of amyloid-beta 1-42 (Aβ42) is an essential pathological feature of Alzheimer's disease (AD), and development of Aβ42 nanomodulators offers a potentially therapeutic approach to AD. Here, we report facile synthesis of the hollow mesocrystalline Prussian blue nanocages (HMPBs), which serve as versatile Aβ42 modulators. Due to the hollow nanostructures and large specific surface area, they can effectively inhibit Aβ42 aggregation by adsorption. They also exhibit robust near-infrared (NIR) photothermal effect for light-to-heat transition, which promotes the depolymerization of Aβ42 fibers. Besides, they display ROS quenching ability to scavenge hydroxyl radicals (•OH) caused by Aβ42 fibers, alleviate cellular oxidative stress, and improve cell survival. This work provides a new kind of Prussian blue nanomaterial for multimodal Aβ modulation.

Construction of Compartmentalized Meso/Micro Spaces in Hierarchically Porous MOFs with Long-Chain Functional Ligands Inspired by Biological Signal Amplification

The creation of spatially coupled meso-/microenvironments with biomimetic compartmentalized functionalities is of great significance to achieve efficient signal transduction and amplification. Herein, using a soft-template strategy, UiO-67-type hierarchically mesoporous metal-organic frameworks (HMMOFs) were constructed to satisfy the requirements of such an artificial system. The key to the successful synthesis of HMUiO-67 is rooted in the utilization of the preformed cerium-oxo clusters as metal precursors, aligning the growth of MOF crystals with the mild conditions required for the self-assembly of the soft template. The adoption of long-chain functional 2,2'-bipyridine-5,5'-dicarboxylic acid ligands not only resulted in larger microporous sizes, facilitating the transport of various cascade reaction intermediates, but also provided anchorages for the introduction of enzyme-mimicking active sites. A cascade amplification system was designed based on the developed HMUiO-67, in which enzyme cascade reactions were initiated and relayed by a target analyte in the separate but coupled meso/micro spaces. As a proof of concept, natural acetylcholinesterase (AChE) and Cu-based laccase mimetics were integrated into HMMOFs, establishing a spatially coupled nanoreactor. The activity of AChE was triggered by the target analyte of carbaryl, while the amplified products of AChE catalysis mediated the activity of biomimetic enzyme in the closely proximate microporous spaces, producing further amplification of detectable signal. This enabled the entire cascade system to respond to minimal carbaryl with a limit of detection as low as approximately 2 nM. Such a model of cascade amplification is expected to set a conceptual guideline for the rational design of various bioreactors, serving as a sensitive response system for quantifying numerous target analytes.

Achievements and Challenges in Surfactants-Assisted Synthesis of MOFs-Derived Transition Metal-Nitrogen-Carbon as a Highly Efficient Electrocatalyst for ORR, OER, and HER

Metal-organic frameworks (MOFs) are excellent precursors for preparing transition metal and nitrogen co-doped carbon catalysts, which have been widely utilized in the field of electrocatalysis since their initial development. However, the original MOFs derived catalysts have been greatly limited in their development and application due to their disadvantages such as metal atom aggregation, structural collapse, and narrow pore channels. Recently, surfactants-assisted MOFs derived catalysts have attracted much attention from researchers due to their advantages such as hierarchical porous structure, increased specific surface area, and many exposed active sites. This review mainly focuses on the synthesis methods of surfactants-assisted MOFs derived catalysts and comprehensively introduces the action of surfactants in MOFs derived materials and the structure-activity relationship between the catalysts and the oxygen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction performance. Apparently, the aims of this review not only introduce the status of surfactants-assisted MOFs derived catalysts in the field of electrocatalysis but also contribute to the rational design and synthesis of MOFs derived catalysts for fuel cells, metal-air cells, and electrolysis of water toward hydrogen production.

Boosting the Strength and Toughness of Polymer Blends via Ligand-Modulated MOFs

Mechanically robust and tough polymeric materials are in high demand for applications ranging from flexible electronics to aerospace. However, achieving both high toughness and strength in polymers remains a significant challenge due to their inherently contradictory nature. Here, a universal strategy for enhancing the toughness and strength of polymer blends using ligand-modulated metal-organic framework (MOF) nanoparticles is presented, which are engineered to have adjustable hydrophilicity and lipophilicity by varying the types and ratios of ligands. Molecular dynamics (MD) simulations demonstrate that these nanoparticles can effectively regulate the interfaces between chemically distinct polymers based on their amphiphilicity. Remarkably, a mere 0.1 wt.% of MOF nanoparticles with optimized amphiphilicity (ML-MOF(5:5)) delivered ≈1.1- and ≈34.1-fold increase in strength and toughness of poly (lactic acid) (PLA)/poly (butylene succinate) (PBS) blend, respectively. Moreover, these amphiphilicity-tailorable MOF nanoparticles universally enhance the mechanical properties of various polymer blends, such as polypropylene (PP)/polyethylene (PE), PP/polystyrene (PS), PLA/poly (butylene adipate-co-terephthalate) (PBAT), and PLA/polycaprolactone (PCL)/PBS. This simple universal method offers significant potential for strengthening and toughening various polymer blends.

Consolidating the Oxygen Reduction with Sub-Polarized Graphitic Fe-N4 Atomic Sites for an Efficient Flexible Zinc-Air Battery

The effectuation of the Zn-air battery (ZAB) is appealing for active and durable catalysts to kinetically drive the sluggish cathodic oxygen reduction reaction (ORR). Atomic metal-Nx-C sites are widely witnessed with Pt-like activity, but their demetalations still severely restrict the durability in ORR. Here we have profiled an ordered hierarchical porous carbon supported Fe-N4 single-atom (FeNC) catalyst by a template derivation method for efficient ORR and flexible ZAB studies. The FeNC structure is observed with a sub-polarized graphitic Fe-N4 coordination with a shortened Fe-N bond for potentially consolidating the ORR, together with the hierarchical porous matrix for kinetical mass transfer. Resultantly, the optimized FeNC catalyst showcases Pt-beyond alkaline ORR activity (E1/2 = 0.95 V) with long-term durability for 100 h, delivering the flexible ZAB device with high power density (251 mW cm-2) and durable cycle life (80 h). This research underscores the criterion in rationalizing active and robust ORR catalysts through metal-nitrogen bond modulation.

Biphasic interface templated synthesis of wrinkled MOFs for the construction of cascade sensing platform based on the encapsulated gold nanoclusters and enzymes

The design and construction of MOFs with flower-like structure could afford sufficient space for the immobilization of guests with large size and interconnected transport channels for their mass diffusion although it remains a challenge. Herein, wrinkled Ce-based hierarchically porous UiO-66 (Ce-WUiO-66) with good crystallinity was successfully synthesized for the first time using bicontinuous emulsion composed of 1-heptanol, water and F127 (PEO106PPO70PEO106) surfactant as a template. F127 played a key role in the formation of emulsions as a stabilizer, and meanwhile its PEO segments interacted with MOF precursors to guide the evolvement of crystallized pore walls. Through controlling the ratios of heptanol to water and the salinity, the distances of the pleat openings and the morphology of the resultant Ce-WUiO-66 were facilely regulated. In virtue of its highly open radial structure, Ce-WUiO-66 could serve as an ideal platform for loading multiple substances to build a cascade sensing system. As a proof of concept, we designed an amino acid (AA) cascade probe by co-immobilizing gold nanoclusters (AuNCs) and LAA oxidase into Ce-WUiO-66. The aggregation-induced-emission enhancement resulted from the encapsulation of AuNCs into Ce-WUiO-66 significantly improved the detection sensitivity and the detection limit of corresponding substrates reached as low as 10-8 M. The proposed biphasic interface assembly strategy is hopefully to provide a new route for the rational design of MOFs with various open pore structure and broaden their potential applications with multiple large-size substances involved besides the currently exemplified cascade sensing platform.

Metal-Organic Frameworks (MOFs): Classification, Synthesis, Modification, and Biomedical Applications

Metal-organic frameworks (MOFs) are a new variety of solid crystalline porous functional materials. As an extension of inorganic porous materials, it has made important progress in preparation and application. MOFs are widely used in various fields such as gas adsorption storage, drug delivery, sensing, and biological imaging due to their high specific surface area, porosity, adjustable pore size, abundant active sites, and functional modification by introducing groups. In this paper, the types of MOFs are classified, and the synthesis methods and functional modification mechanisms of MOFs materials are summarized. Finally, the application prospects and challenges of metal-organic framework materials in the biomedical field are discussed, hoping to promote their application in multidisciplinary fields.

Ultrastable hierarchically porous nucleotide-based MOFs and their use for enzyme immobilization and catalysis

Immobilization of free enzymes facilitates their recovery and reuse, while also enhances their enzymatic characteristics. Hierarchically porous metal-organic frameworks (HP-MOFs) are promising candidates for enzyme immobilization. However, fabrication of HP-MOFs with more kinds of components as ligands is still a challenge. Herein, ultrastable crystalline MOFs with micro-, meso- and macroporous structure were constructed using guanosine 5'-monophosphate (GMP) as organic ligand through templated emulsification method. HP-MOFs crystals with the near rhomb-like, rod-like and slab-like morphology were interestingly obtained from Zn2+, Cu2+ and Cd2+ respectively. The HP-MOFs immobilized enzymes exhibited an enhanced enzymatic activity and stability. In addition, the immobilized CALB (Candida antarctica lipase B) showed great glycerolysis and esterification performances for glycerides preparation, with diacylglycerols (DAG) content over 60 wt% and triacylglycerols (TAG) content over 90 wt% obtained respectively from glycerolysis and esterification. Moreover, it retained 82.32 % of its initial glycerolysis activity after six cycles of reuse in glycerolysis. The present study will provide clues and show new horizons to explore new organic ligands for HP-MOFs fabrication, as well as to expand the applications of HP-MOFs and their supported enzymes.

Luminescent Ln-MOFs for Chemical Sensing Application on Biomolecules

At present, the application of rare-earth organic frameworks (Ln-MOFs) in fluorescence sensing has entered rapid development and shown great potential in various analytical fields, such as environmental analysis, food analysis, drug analysis, and biological and clinical analysis by utilizing their internal porosity, tunable structural size, and energy transfer between rare-earth ions, ligands, and photosensitizer molecules. In addition, because the luminescence properties of rare-earth ions are highly dependent on the structural details of the coordination environment surrounding the rare-earth ions, and although their excitation lifetimes are long, they are usually not burst by oxygen and can provide an effective platform for chemical sensing. In order to further promote the development of fluorescence sensing technology based on Ln-MOFs, we summarize and review in detail the latest progress of the construction of Ln-MOF materials for fluorescence sensing applications and related sensor components, including design strategies, preparation methods, and modification considerations and initially propose the future development prospects and prospects.

Nanoengineering Multilength-Scale Porous Hierarchy in Mesoporous Metal-Organic Framework Single Crystals

Developing a reliable method for constructing mesoporous metal-organic frameworks (MOFs) with single-crystalline forms remains a challenging task despite numerous efforts. This study presents a solvent-mediated assembly method for fabricating zeolitic imidazolate framework (ZIF) single-crystal nanoparticles with a well-defined micro-mesoporous structure using polystyrene-block-poly(ethylene oxide) diblock copolymer micelles as a soft-template. The precise control of particle sizes, ranging from 85 to 1200 nm, is achieved by regulating nucleation and crystal growth rates while maintaining consistent pore diameters in mesoporous nanoparticles and a rhombohedral dodecahedron morphology. Furthermore, this study presents a robust platform for nanoarchitecturing to prepare hierarchically porous materials (e.g., core-shell and hollow structures), including microporous ZIF@mesoporous ZIF, hollow mesoporous ZIF, and mesoporous ZIF@mesoporous ZIF. Such a multimodal pore design, ranging from microporous to microporous/mesoporous and further micro-/meso-/macroporous, provides significant evidence for the future possibility of the structural design of MOFs.

Hierarchically Micro-, Meso-, and Macro-Porous MOF Nanosystems for Localized Cross-Scale Dual-Biomolecule Loading and Guest-Carrier Cooperative Anticancer Therapy

Mass transfer of bulky molecules, e.g., bioenzymes, particularly for cross-scale multibiomolecules, imposes serious challenges for microporous metal-organic frameworks (MOFs). Here, we create a hierarchically porous MOF heterostructure featuring highly region-ordered micro-, meso-, and macro-pores by growing a microporous ZIF-8 shell onto a hollow Prussian blue core through an epitaxial growth strategy. This allows for localized loading of large bioenzyme glucose oxidase (GOx) and small drug 5-fluorouracil (5-FU) within specific pores simultaneously and triggers unique guest-carrier cooperative anticancer capabilities. The stable ZIF-8 outer layer effectively blocks the core pores, preventing the undesired leakage of GOx into normal tissues. The acidity-induced ZIF-8 degradation gradually releases Zn2+ and loaded 5-FU for chemotherapy under acidic tumor microenvironments. With the loss of the shielding effect of the ZIF-8 coating, the released GOx depletes intratumoral glucose (Glu) for starvation therapy. Notably, an accelerated cascade reaction occurs between ZIF-8 decomposition and GOx release, facilitated by the modulator factor of Glu. This culminates in the realization of synergistic cancer therapy, as comprehensively demonstrated by in vitro and in vivo experiments, as well as transcriptome sequencing analyses. Our work not only introduces a hierarchically porous MOF heterostructure with highly region-ordered pores but also provides a perspective for guest-carrier cooperative anticancer therapy.

Synthetic and analytical considerations for the preparation of amorphous metal-organic frameworks

Metal-organic frameworks (MOFs) are hybrid porous materials presenting several tuneable properties, allowing them to be utilised for a wide range of applications. To date, focus has been on the preparation of novel crystalline MOFs for specific applications. Recently, interest in amorphous MOFs (aMOFs), defined by their lack of correlated long-range order, is growing. This is due to their potential favourable properties compared to their crystalline equivalents, including increased defect concentration, improved processability and gas separation ability. Direct synthesis of these disordered materials presents an alternative method of preparation to post-synthetic amorphisation of a crystalline framework, potentially allowing for the preparation of aMOFs with varying compositions and structures, and very different properties to crystalline MOFs. This perspective summarises current literature on directly synthesised aMOFs, and proposes methods that could be utilised to modify existing syntheses for crystalline MOFs to form their amorphous counterparts. It outlines parameters that could discourage the ordering of crystalline MOFs, before examining the potential properties that could emerge. Methodologies of structural characterisation are discussed, in addition to the necessary analyses required to define a topologically amorphous structure.

Textural Precursor Compositions Harvested for Independent Signal Generators: Scaling Micron-Sized Flower-Like Metal-Organic Frameworks as Amplifying Units for Dual-Mode Glycoprotein Assay

In this work, a micron-sized flower-like metal-organic frameworks (MOFs)-based boronate-affinity sandwich-type immunoassay was fabricated for the dual-mode glycoprotein assay. For proof of concept, the flower-like MOFs were synthesized from transition Cu nodes and tetrakis (4-carboxyphenyl) porphyrin (TCPP) ligands by spontaneous standing assembly. In addition, the specificity toward glycoprotein involved the antigen recognition as well as covalent bonding via the boronate-glycan affinity, and the immediate signal responses were initiated by textural decomposition of the flower-like MOFs. Intriguingly, Cu nodes, of which the valence state is dominant by CuI species, can endow the Fenton-like catalytic reaction of the fluorogenic substrate for generating fluorescence signals. For benefits, TCPP ligands, in which each TCPP molecule has four guest donors, can provide multiple valences for the assembly of cyclodextrin-capped gold nanoparticles via host-guest interaction for colorimetry output. Albeit important, the scaling micrometer patterns for the flower-like MOFs carrying numerous Cu nodes and TCPP ligands can also function as amplifying units, signifying the output signal. The detection limit of the dual-mode glycoprotein assay can reach 10.5 nM for the fluorescence mode and 18.7 nM for the colorimetry mode, respectively. Furthermore, the merits of harvesting different signal generators toward the multimodal readout patterns can allow the mutual verification and make the analytical results more reliable. Collectively, our proposed assay may offer a new idea in combining the inherent textural merits from MOFs for dual signal generators, which can also emphasize accurate detection capability for glycoprotein assay.

Hierarchical porous carbon materials for lithium storage: preparation, modification, and applications

Secondary battery as an efficient energy conversion device has been highly attractive for alleviating the energy crisis and environmental pollution. Hierarchical porous carbon (HPC) materials with multiple sizes pore channels are considered as promising materials for energy conversion and storage applications, due to their high specific surface area and excellent electrical conductivity. Although many reviews have reported on carbon materials for different fields, systematic summaries about HPC materials for lithium storage are still rare. In this review, we first summarize the main preparation methods of HPC materials, including hard template method, soft template method, and template-free method. The modification methods including porosity and morphology tuning, heteroatom doping, and multiphase composites are introduced systematically. Then, the recent advances in HPC materials on lithium storage are summarized. Finally, we outline the challenges and future perspectives for the application of HPC materials in lithium storage.

Constructing ordered and tunable extrinsic porosity in covalent organic frameworks via water-mediated soft-template strategy

As one of the most attractive methods for the synthesis of ordered hierarchically porous crystalline materials, the soft-template method has not appeared in covalent organic frameworks (COFs) due to the incompatibility of surfactant self-assembly and guided crystallization process of COF precursors in the organic phase. Herein, we connect the soft templates to the COF backbone through ionic bonds, avoiding their crystallization incompatibilities, thus introducing an additional ordered arrangement of soft templates into the anionic microporous COFs. The ion exchange method is used to remove the templates while maintaining the high crystallinity of COFs, resulting in the construction of COFs with ordered hierarchically micropores/mesopores, herein named OHMMCOFs (OHMMCOF-1 and OHMMCOF-2). OHMMCOFs exhibit significantly enhanced functional group accessibility and faster mass transfer rate. The extrinsic porosity can be adjusted by changing the template length, concentration, and ratio. Cationic guanidine-based COFs (OHMMCOF-3) are also constructed using the same method, which verifies the scalability of the soft-template strategy. This work provides a path for constructing ordered and tunable extrinsic porosity in COFs with greatly improved mass transfer efficiency and functional group accessibility.

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.

Hierarchically Porous Covalent Organic Frameworks: Synthesis Methods and Applications

Covalent organic frameworks (COFs) with high porosity have garnered considerable interest for various applications owing to their robust and customizable structure. However, conventional COFs are hindered by their narrow pore size, which poses limitations for applications such as heterogeneous catalysis and guest delivery that typically involve large molecules. The development of hierarchically porous COF (HP-COF), featuring a multi-scale aperture distribution, offers a promising solution by significantly enhancing the diffusion capacity and mass transfer for larger molecules. This review focuses on the recent advances in the synthesis strategies of HP-COF materials, including topological structure design, in-situ templating, monolithic COF synthesis, defect engineering, and crystalline self-transformation. The specific operational principles and affecting factors in the synthesis process are summarized and discussed, along with the applications of HP-COFs in heterogeneous catalysis, toxic component treatment, optoelectronics, and the biomedical field. Overall, this review builds a bridge to understand HP-COFs and provides guidance for further development of them on synthesis strategies and applications.

Strain-Induced Heteromorphosis Multi-Cavity Cages: Tension-Driven Self-Expansion Strategy for Controllable Enhancement of Complexity in Supramolecular Assembly

Coordinative supramolecular cages with adjustable cavities have found extensive applications in various fields, but the cavity modification strategies for multi-functional structures are still challenging. Here, we present a tension-driven self-expansion strategy for construction of multi-cavity cages with high structural complexity. Under the regulation of strain-induced capping ligands, unprecedented heteromorphosis triple-cavity cages S2 /S4 were obtained based on a metallo-organic ligand (MOL) scaffold. The heteromorphosis cages exhibited significant higher cavity diversity than the homomorphous double-cavity cages S1 /S3 ; all of the cages were thoroughly characterized through various analytical techniques including (1D and 2D) NMR, ESI-MS, TWIM-MS, AFM, and SAXS analyses. Furthermore, the encapsulation of porphyrin in the cavities of these multi-cavity cages were investigated. This research opens up new possibilities for the architecture of heteromorphosis supramolecular cages via precisely controlled "scaffold-capping" assembly with preorganized ligands, which could have potential applications in the development of multifunctional structures with higher complexity.

Infiltration of porcine pancreatic lipase into magnetic hierarchical mesoporous UiO-66-NH2 metal-organic frameworks for efficient detoxification of patulin from apple juice

Patulin (PAT) is a mycotoxin known to globally contaminate fruits. The economic losses and health hazards caused by PAT desires a safe and efficient strategy for detoxifying PAT. Here, a magnetic core-shell hierarchical mesoporous metal-organic framework (Fe3O4@HMUiO-66-NH2) was synthesized via a salt-assisted nanoemulsion guided assembly method. This mesoporous structure (centered at 4.25 nm) allowed porcine pancreatic lipase (PPL) to infiltrate into the MOF shell at an immobilized amount of 255 mg/g, providing protection for PPL and enabling rapid separation and recovery. Compared with free PPL, PPL/Fe3O4@HMUiO-66-NH2 at 70 °C possessed 4.7 folds improved thermal stability in terms of half-life. The detoxification rates of immobilized enzyme for PAT in neutral water, acidic water, and apple juice were 99.6%, 60.9%, and 52.6%, respectively. Moreover, the so designed PPL/Fe3O4@HMUiO-66-NH2 showed extraordinary storage stability, reusability, and biocompatibility. Crucially, the quality of apple juice did not change significantly after PPL/Fe3O4@HMUiO-66-NH2 treatment, which facilitated its application in apple juice. The magnetic core-shell mesoporous structure along with the revealed mechanism of immobilized enzyme detoxification of PAT provide tremendous opportunity for designing a safe and efficient PAT detoxification method.

Atomically Dispersed ZnN4 Sites Anchored on P-Functionalized Carbon with Hierarchically Ordered Porous Structures for Boosted Electroreduction of CO2

Tuning the coordination structures of metal sites is intensively studied to improve the performances of single-atom site catalysts (SASC). However, the pore structure of SASC, which is highly related to the accessibility of active sites, has received little attention. In this work, single-atom ZnN4 sites embedded in P-functionalized carbon with hollow-wall and 3D ordered macroporous structure (denoted as H-3DOM-ZnN4 /P-C) are constructed. The creation of hollow walls in ordered macroporous structures can largely increase the external surface area to expose more active sites. The introduction of adjacent P atoms can optimize the electronic structure of ZnN4 sites through long-rang regulation to enhance the intrinsic activity and selectivity. In the electrochemical CO2 reduction reaction, H-3DOM-ZnN4 /P-C exhibits high CO Faradaic efficiency over 90% in a wide potential window (500 mV) and a large turnover frequency up to 7.8 × 104  h-1 at -1.0 V versus reversible hydrogen electrode, much higher than its counterparts without the hierarchically ordered structure or P-functionalization.

Anisotropic Interface Successive Assembly for Bowl-Shaped Metal-Organic Framework Nanoreactors with Precisely Controllable Meso-/Microporous Nanodomains

Colloidal metal-organic framework (MOF) nanoparticles, with tailored asymmetric nanoarchitectures and hierarchical meso-/microporosities, have significant implications in high-performance nanocatalysts, nanoencapsulation carriers, and intricate assembly architectures. However, the methodology that could achieve precise control over the anisotropic growth of asymmetric MOF particles with tailored distributions of meso- and microporous regions has not yet been established. In this study, we introduce a facile anisotropic interface successive assembly approach to synthesize asymmetric core-shell MOF (ZIF-67) nanobowls with worm-like mesopores in the core and intrinsic micropores in the shell. Our synthesis pathway relies on anisotropic nucleation of mesoporous MOF nanohemispheres on emulsion interfaces through the cooperative assembly of surfactants and MOF precursors. This is followed by the growth of microporous MOF layers on both interfaces of mesoporous cores and emulsion droplets, resulting in a hierarchically porous core-shell nanostructure. By utilizing this multi-interface-driven approach, we enable the creation of diverse geometries and distributions of mesopores and micropores in asymmetric MOF nanoarchitectures. The obtained bowl-like meso-/microporous core-shell ZIF-67 particles exhibit enhanced catalytic activity for CO2 cycloaddition, attributed to reactant accumulation within the bowl-like architecture, active site accessibility in the open mesoporous core, and improved structural stability. Overall, our study provides insights and inspiration for exploring the intricate asymmetric nanostructures of hierarchically porous MOFs with diverse potential applications.

Hierarchical Yolk-Shell Porous Ionic Liquids with Lower Viscosity for Efficient C3H6/C3H8 Adsorption and Separation

Yolk-shell metal-organic framework (YS-MOF) liquids are candidate materials in large-size species with high-efficiency separation, owing to their hierarchical porosity, faster mass transfer, better compatibility, and higher solution processability than MOF liquids with micropores. Nevertheless, facile synthesis strategies of yolk-shell porous ionic liquids (YSPILs) with regulations of size and morphology are an ongoing challenge. Herein, we propose a general strategy to construct YSPILs based on Z67@PDA with tunable core sizes and morphologies. Benefiting from the unique hierarchical yolk-shell structure, as-prepared YSPILs exhibit promise in C3H6/C3H8 capture and separation with the increased sizes of core in yolk-shell ZIF-67@PDA. Advanced YS-MOF liquids have improved the adsorption properties and increased our ability to tailor chemical composition and pore architecture. Impressively, the adsorption capacity of C3H6 and C3H8 of YSPILs exhibits an approximately 3-fold enhancement compared with that of the neat ILs, confirming that the accessible porosities are retained. Effective C3H6/C3H8 separation performance of YSPILs over PILs based on ZIF-67, revealing the hierarchical porosity of YS-Z67@PDA liquids, benefits larger-size gas separation. Therefore, we believe that this work can not only help us to rationally design novel hierarchically porous ionic liquids but also promote candidate applications in large-size species separation, catalysis, and nanoreactors.

Recent Advances in Multifunctional Reticular Framework Nanoparticles: A Paradigm Shift in Materials Science Road to a Structured Future

Porous organic frameworks (POFs) have become a highly sought-after research domain that offers a promising avenue for developing cutting-edge nanostructured materials, both in their pristine state and when subjected to various chemical and structural modifications. Metal-organic frameworks, covalent organic frameworks, and hydrogen-bonded organic frameworks are examples of these emerging materials that have gained significant attention due to their unique properties, such as high crystallinity, intrinsic porosity, unique structural regularity, diverse functionality, design flexibility, and outstanding stability. This review provides an overview of the state-of-the-art research on base-stable POFs, emphasizing the distinct pros and cons of reticular framework nanoparticles compared to other types of nanocluster materials. Thereafter, the review highlights the unique opportunity to produce multifunctional tailoring nanoparticles to meet specific application requirements. It is recommended that this potential for creating customized nanoparticles should be the driving force behind future synthesis efforts to tap the full potential of this multifaceted material category.

Ce-based solid-phase catalysts for phosphate hydrolysis as new tools for next-generation nanoarchitectonics

This review comprehensively covers synthetic catalysts for the hydrolysis of biorelevant phosphates and pyrophosphates, which bridge between nanoarchitectonics and biology to construct their interdisciplinary hybrids. In the early 1980s, remarkable catalytic activity of Ce4+ ion for phosphate hydrolysis was found. More recently, this finding has been extended to Ce-based solid catalysts (CeO2 and Ce-based metal-organic frameworks (MOFs)), which are directly compatible with nanoarchitectonics. Monoesters and triesters of phosphates, as well as pyrophosphates, were effectively cleaved by these catalysts. With the use of either CeO2 nanoparticles or elegantly designed Ce-based MOF, highly stable phosphodiester linkages were also hydrolyzed. On the surfaces of all these solid catalysts, Ce4+ and Ce3+ coexist and cooperate for the catalysis. The Ce4+ activates phosphate substrates as a strong acid, whereas the Ce3+ provides metal-bound hydroxide as an eminent nucleophile. Applications of these Ce-based catalysts to practical purposes are also discussed.

Thermocatalytic Conversion of CO2 to Valuable Products Activated by Noble-Metal-Free Metal-Organic Frameworks

Thermocatalysis of CO2 into high valuable products is an efficient and green method for mitigating global warming and other environmental problems, of which Noble-metal-free metal-organic frameworks (MOFs) are one of the most promising heterogeneous catalysts for CO2 thermocatalysis, and many excellent researches have been published. Hence, this review focuses on the valuable products obtained from various CO2 conversion reactions catalyzed by noble-metal-free MOFs, such as cyclic carbonates, oxazolidinones, carboxylic acids, N-phenylformamide, methanol, ethanol, and methane. We classified these published references according to the types of products, and analyzed the methods for improving the catalytic efficiency of MOFs in CO2 reaction. The advantages of using noble-metal-free MOF catalysts for CO2 conversion were also discussed along the text. This review concludes with future perspectives on the challenges to be addressed and potential research directions. We believe that this review will be helpful to readers and attract more scientists to join the topic of CO2 conversion.

Interfacial chemistries in metal-organic framework (MOF)/covalent-organic framework (COF) hybrids

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have been attracting tremendous attention in various applications due to their unique structural properties. Recent interest has been focused on their combination as hybrids to enable the engineering of new classes of frameworks with complementary properties. This review gives a comprehensive summary on the interfacial chemistries in MOF/COF hybrids, which play critical roles in their hybridization. The challenges and perspectives in the field of MOF/COF hybrids are also provided to inspire more efforts in diversifying this hybrid family and their cross-disciplinary applications.

Polyoxometalate-Bridged Synthesis of Superstructured Mesoporous Polymers and Their Derivatives for Sodium-Iodine Batteries

Despite the impressive progress in mesoporous materials over past decades, for those precursors having no well-matched interactions with soft templates, there are still obstacles to be guided for mesoporous structure via soft-template strategies. Here, a polyoxometalate-assisted co-assembly route is proposed for controllable construction of superstructured mesoporous materials by introducing polyoxometalates as bifunctional bridge units, which weakens the self-nucleation tendency of the precursor through coordination interactions and simultaneously connects the template through the induced dipole-dipole interaction. By this strategy, a series of meso-structured polymers, featuring highly open radial mesopores and dendritic pore walls composed of continuous interwoven nanosheets can be facilely obtained. Further carbonization gave rise to nitrogen-doped hierarchical mesoporous carbon decorated uniformly with ultrafine γ-Mo2 N nanoparticles. Density functional theory proves that nitrogen-doped carbon and γ-Mo2 N can strongly adsorb polyiodide ions, which effectively alleviate polyiodide dissolving in organic electrolytes. Thereby, as the cathode materials for sodium-iodine batteries, the I2 -loaded carbonaceous composite shows a high specific capacity (235 mA h g-1 at 0.5 A g-1 ), excellent rate performance, and cycle stability. This work will open a new venue for controllable synthesis of new hierarchical mesoporous functional materials, and thus promote their applications toward diverse fields.

Construction of rose flower-like NiCo-LDH electrode derived from bimetallic MOF for highly sensitive electrochemical sensing of hydrazine in food samples

It is necessary to efficient detection hydrazine in food. Exploring highly sensitive, low-cost and fast response electrochemical hydrazine sensing methods has been a challenge in this field. In this paper, a conformal transformation method is used to prepare rose flower-like NiCo-LDH derivating from the bimetallic NiCo-MOFs, and the N₂H₄ sensing platform with a large electrocatalytic area, high conductivity and good stability was constructed. Based on the synergy between Ni and Co and the remarkable catalytic activity of the rough 3D flower-like structure, the N₂H₄ sensor has a linear response in the concentration range of 0.001-1 mmol/L and 1-7 mmol/L, with a sensitivity of 5342 μA L mmol^-1 cm^-2 and 2965 μA L mmol^-1 cm^-2 (S/N = 3), respectively, and low limit of detection of 0.043 μmol/L. This study opens a new door for the successful application of electrochemical sensors to detect N₂H₄ in real food samples.

Hierarchical porous Fe-N/C@surfactant composites synthesized by a surfactant-assisted strategy as high-performance bifunctional oxygen electrodes for rechargeable zinc-air batteries

Herein, a soft-template strategy involving the cationic surfactants has been successfully applied to size-controlled synthesis of hierarchical porous Fe-N/C for the first time. Specifically, a small amount of Fe and cationic surfactants can be uniformly doped into the zinc-based zeolite imidazole framework (ZIF-8) crystal particles and the cationic surfactants play a critical role in the formation of hierarchically porous Fe-ZIF-8@surfactant precursors. When the Fe-ZIF-8@surfactant is subsequently pyrolyzed, atomically dispersed Fe-N_x coordination structures can be in-situ converted to Fe-N/C, while the cationic surfactants decompose to form a carbon matrix to encapsulate the active sites, thereby preventing the aggregation of nanoparticles to a certain extent. As a result, the combined Fe nanocrystals and atomically dispersed Fe-N_x in the graphitic carbon matrix generate a synergistic effect to boost the electrocatalytic behaviors with a more positive half-wave potential (0.92 V) for oxygen reduction reaction (ORR) and a lower overpotential (420 mV at 10 mA cm^-2) for oxygen evolution reaction (OER). As a proof of concept, the Fe-N/C@TTAB based zinc-air batteries (ZABs) present an outstanding peak power density (107.9 mW cm^-2) and a superior specific capacity (706.3 mAh g^-1) with robust cycling stability over 900 cycles for 150 h, which are better than the commercial Pt/C + IrO₂ based ZABs.

Improved stability and activity of laccase through de novo and post-synthesis immobilization on a hierarchically porous metal-organic framework (ZIF-8)

Porous materials such as metal-organic frameworks (MOFs) are considered to be suitable materials for immobilizing enzymes to improve their stability. However, conventional MOFs reduce the enzymes' catalytic activity due to difficulties with mass transfer and diffusing reactants after their micropores are occupied by enzyme molecules. To address these issues, a novel hierarchically structured zeolitic imidazolate framework-8 (HZIF-8) was prepared to study the effects of different laccase immobilization approaches such as the post-synthesis (LAC@HZIF-8-P) and de novo (LAC@HZIF-8-D) immobilization of catalytic activities for removing 2,4-dichlorophenol (2,4-DCP). The results showed higher catalytic activity for the laccase-immobilized LAC@HZIF-8 prepared using different methods than for the LAC@MZIF-8 sample, with 80% of 2,4-DCP removed under optimal conditions. These results could be attributable to the multistage structure of HZIF-8. The LAC@HZIF-8-D sample was stable and superior to LAC@HZIF-8-P, maintaining a 2,4-DCP removal efficiency of 80% after three recycles and demonstrating superior laccase thermostability and storage stability. Moreover, after loading with copper nanoparticles, the LAC@HZIF-8-D approach exhibited a 2,4-DCP removal efficiency of 95%, a promising finding for its potential use in environmental purification.

Morphology-Engineering Construction of Anti-Aggregated Co/N-Doped Hollow Carbon from Metal-Organic Frameworks for Efficient Biomass Upgrading

The controlled pyrolysis of metal/carbon-containing precursors is commonly used for fabricating multifunctional metal/carbon-based catalysts, nevertheless, the inevitable agglomeration of these precursors in pyrolysis is extremely negative for efficient catalysis. This study reports the first example of suppressing the interfacial fusion and agglomeration of metal/carbon-based catalyst in its pyrolysis-involved fabrication process by developing a facile morphology-engineering strategy. Metal-organic framework precursors are chosen as a proof of concept and five Co/N-doped hollow carbons with different morphologies (rhombic dodecahedron, cube, plate, interpenetration twin, and rod) are synthesized via the pyrolysis of their corresponding core-shell ZIF-8@ZIF-67 precursors. It is demonstrated that the interpenetration twin precursor shows the minimum interfacial contact of interparticles due to its partly-concave morphology with abundant facets, which endows it with the best resistibility from interfacial fusion and thus aggregation of interparticles during pyrolysis. Benefiting from its unique anti-aggregated structure with high specific surface area, abundant fully-exposed active sites, and good dispersibility, the resultant 36-facet Co/N-doped hollow carbon exhibit remarkably improved catalytic property for biomass upgrading as compared with its aggregated counterparts. This study highlights the crucial role of engineering morphology to prevent metal/carbon-containing precursors from detrimental agglomeration during pyrolysis, demonstrating a new approach to constructing anti-aggregated metal/carbon-based catalysts.

Metal Organic Framework Cubosomes

We demonstrate a general strategy for the synthesis of ordered bicontinuous-structured metal organic frameworks (MOFs) by using polymer cubosomes (PCs) with a double primitive structure (Im 3 ‾ ${\bar{3}}$ m symmetry) as the template. The filling of MOF precursors in the open channel of PCs, followed by their coordination and removal of the template, generates MOF cubosomes with a single primitive topology (Pm 3 ‾ ${\bar{3}}$ m) and average mesopore diameters of 60-65 nm. Mechanism study reveals that the formation of ZIF-8 cubosomes undergoes a new MOF growth process, which involves the formation of individual MOF seeds in the template, their growth and eventual fusion into the cubosomes. Their growth kinetics follows the Avrami equation with an Avrami exponent of n=3 and a growth rate of k=1.33×10^-4 , indicating their fast 3D heterogeneous growth mode. Serving as a bioreactor, the ZIF-8 cubosomes show high loading of trypsin enzyme, leading to a high catalytic activity in the proteolysis of bovine serum albumin.

Ordered Macro-Microporous Single Crystals of Covalent Organic Frameworks with Efficient Sorption of Iodine

Fashioning microporous covalent organic frameworks (COFs) into single crystals with ordered macropores allows for an effective reduction of the mass transfer resistance and the maximum preservation of their intrinsic properties but remains unexplored. Here, we report the first synthesis of three-dimensional (3D) ordered macroporous single crystals of the imine-linked 3D microporous COFs (COF-300 and COF-303) via a template-assisted modulated strategy. In this strategy, COFs crystallized within the sacrificial colloidal crystal template, assembled from monodisperse polystyrene microspheres, and underwent an aniline-modulated amorphous-to-crystalline transformation to form large single crystals with 3D interconnected macropores. The effects of the introduced macroporous structure on the sorption performances of COF-300 single crystals were further probed by iodine. Our results indicate that iodine adsorption occurred in micropores of COF-300 but not in the introduced macropores. Accordingly, the iodine adsorption capacity of COF single crystals was governed by their micropore accessibility. The relatively long diffusion path in the non-macroporous COF-300 single crystals resulted in a limited micropore accessibility (48.4%) and thus a low capacity in iodine adsorption (1.48 g·g^-1). The introduction of 3D ordered macropores can greatly shorten the microporous diffusion path in COF-300 single crystals and thus render all their micropores fully accessible in iodine adsorption with a capacity (3.15 g·g^-1) that coincides well with the theoretical one.

The Advanced Synthesis of MOFs-Based Materials in Photocatalytic HER in Recent Three Years

Since the advent of metal–organic frameworks (MOFs), researchers have paid extensive attention to MOFs due to their determined structural composition, controllable pore size, and diverse physical and chemical properties. Photocatalysis, as a significant application of MOFs catalysts, has developed rapidly in recent years and become a research hotspot continuously. Various methods and approaches to construct and modify MOFs and their derivatives can not only affect the structure and morphology, but also largely determine their properties. Herein, we summarize the advanced synthesis of MOFs-based materials in the field of the photocatalytic decomposition of water to produce hydrogen in the recent three years. The main contents include the overview of the novel synthesis strategies in four aspects: internal modification and structure optimization of MOFs materials, MOFs/semiconductor composites, MOFs/COFs-based hybrids, and MOFs-derived materials. In addition, the problems and challenges faced in this direction and the future development goals were also discussed. We hope this review will help deepen the reader’s understanding and promote continued high-quality development in this field.

Fabrication of Multilayered Two-Dimensional Micelles and Fibers by Controlled Self-Assembly of Rod-Coil Block Copolymers

Fabricating hierarchical nanomaterials by self-assembly of rod-coil block copolymers attracts great interest. However, the key factors that affect the formation of the hierarchical nanomaterials have not been thoroughly researched. Herein, we have synthesized two diblock copolymers composed of poly(3-hexylthiophene) (P3HT) and polyethylene glycol (PEG). Through a heating, cooling, and aging process, a series of multilayered hierarchical micelles and fibers were prepared in alcoholic solutions. The transition from fibers to hierarchical micelles are strictly influenced by the strength of the π-π stacking interaction, the PEG chain length, and solvent. In isopropanol, the P3HT₂₂-b-PEG₄₃ could self-assemble into hierarchical micelles composed of several two-dimensional (2D) laminar layers, driven by the π-π stacking interaction and van der Waals force. The P3HT₂₂-b-PEG₄₃ could not self-assemble into well-defined nanostructures in methanol and ethanol, but could self-assemble into fibers in isobutanol. However, the P3HT₂₂-b-PEG₁₁₃ with a longer corona block only self-assembled into fibers in four alcoholic solutions, due to the increase in dissolving capacity and steric hindrance. The sizes and the size distributions of the nanostructures both increased with the increase in polymer concentration and the decrease in solvent polarity. This study shows a method to fabricate the hierarchical micelles.