Synthetic design of functional boron imidazolate frameworks

Effect of Boron-Doping on Gate-Opening CO2 Adsorption in Zinc-Benzimidazolate Coordination Networks

Flexible metal-organic frameworks (MOFs) have attracted much attention as selective gas adsorption and storage. This report describes boron doping in zeolitic imidazolate framework-7 (B-ZIF-7), which exhibits reversible phase transition during CO2 adsorption/desorption. We have successfully prepared B-ZIF-7 coordination networks using boron-bridged benzimidazolate (B(bim)4-) as organic ligands. Powder X-ray diffraction (PXRD) measurements and infrared spectroscopy revealed that B-ZIF-7 has a crystal structure similar to that of ZIF-7 while containing boron bridging in the coordination network. Since B-ZIF-7 forms a cationic coordination network, the guest anions are encapsulated within the pore. CO2 adsorption/desorption measurements at 300 K showed that B-ZIF-7(NO3), which contains nitrate ions (NO3-) as guest anions in its pores, exhibits a S-shaped CO2 adsorption/desorption isotherm, which is characteristic of gate-opening type MOFs. Compared with ZIF-7, B-ZIF-7(NO3) has superior CO2 adsorption capacity in the low-pressure and superior CO2 storage capacity. The CO2 adsorption and desorption behavior of B-ZIF-7(NO3) was analyzed by in situ temperature-controlled PXRD measurements and thermogravimetric analysis under a CO2 atmosphere, and a reversible phase transition was observed. We have also successfully prepared B-ZIF-7(Cl) and B-ZIF-7(OTf) (OTf = CF3SO3-) with different guest anions. The CO2 adsorption/desorption behaviors of B-ZIF-7(Cl) and B-ZIF-7(OTf) were significantly different from those of B-ZIF-7(NO3) and ZIF-7. B-ZIF-7(Cl) showed gate opening at a higher pressure than ZIF-7, and B-ZIF-7(OTf) did not show S-shaped CO2 adsorption isotherm and showed adsorption behavior in micropores. These results indicate that the CO2 adsorption behavior of B-ZIF-7 depends on the interaction between the guest anions and CO2 molecules or the cationic framework and the bulkiness of the guest anions. Boron doping in a coordination network with boron-bridged imidazolate ligands is a promising strategy to increase the gas adsorption capability of porous materials.

Experimental Investigation of Thermodynamic Stabilization in Boron Imidazolate Frameworks (BIFs) Synthesized by Mechanochemistry

This study experimentally explores the energetics for the formation of boron-imidazolate frameworks (BIFs), which are synthesized by mechanochemistry. The topologically similar frameworks employ the same tetratopic linker based on tetrakis(imidazolyl)boric acid but differ in the monovalent cation metal nodes. This permits assessment of the stabilizing effect of metal nodes in frameworks with sodalite (SOD) and diamondoid (dia) topologies. The enthalpy of formation from endmembers (metal oxide and linker), which define thermodynamic stability of the structures, has been determined by use of acid solution calorimetry. The results show that heavier metal atoms in the node promote greater energetic stabilization of denser structures. Overall, in BIFs the relation between cation descriptors (ionic radius and electronegativity) and thermodynamic stability depends on framework topology. Thermodynamic stability increases with the metallic character of the cation employed as the metal node, independent of the framework topology. The results suggest unifying aspects for thermodynamic stabilization across MOF systems.

Advanced BIFs with Co, B, N, and S for Electrocatalytic Oxygen Reduction and Oxygen Evolution Reactions

In this work, a new alkaline-stable boron imidazolate framework (BIF-90) was rationally designed and successfully synthesized by solvothermal reaction. Due to its potential electrocatalytic active sites (Co, B, N, and S) and chemical stabilities, BIF-90 was explored as a bifunctional electrocatalyst toward electrochemical oxygen reactions, namely, oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). This work will open new avenues toward the design of stable, cheap, and more active BIFs as bifunctional catalysts.

Metal-organic framework-based self-healing hydrogel fiber random lasers

Metal-organic frameworks (MOFs), which have well-defined nanoporous skeletons and whose natural structure can work as optical resonant cavities, are emerging as ideal platforms for constructing micro/nanolasers. However, lasing generated from the light oscillating inside a defined MOFs' cavity usually suffers the drawback of the lasing performance being difficult to maintain once the cavity is destroyed. In this work, we report a MOF-based self-healing hydrogel fiber random laser (MOF-SHFRL) that can withstand extreme damage. The optical feedback of MOF-SHFRLs does not depend on the light reflection inside the MOF cavity but comes from the multiple scattering effects from the MOF nanoparticles (NPs). The hydrogel fiber's one-dimensional waveguide structure also permits confined directional lasing transmission. Based on such an ingenious design, a robust random lasing is achieved without worrying about the destruction of the MOF NPs. More interestingly, the MOF-SHFRL demonstrates excellent self-healing ability without any external stimulation: it can fully recover its initial morphology and lasing performance even when totally broken (e.g., cut into two parts). The lasing threshold also remains stable, and the optical transmission capability can recover by more than 90% after multiple breaks and self-healing processes. These results indicate that the MOF-SHFRL is a highly stable optical device that can be expected to play a significant role in environmental monitoring, intelligent sensing, and other aspects under extreme conditions.

Fine-Tuning Tridentate Ligands for the Construction of Nanotube-Based Boron Imidazolate Frameworks with High Chemical Stability

Two unusual nanotube-based boron imidazolate frameworks (BIF-134 and BIF-135) were synthesized by a dual-ligand synthetic strategy under solvothermal conditions. In the structure of BIF-134 ([Co(BH(2-mim)₃)(BTC)_1/3](HBH(2-mim)₃)_1/3(NMA); 2-mim = 2-methylimidazole, NMA = N-methylacetamide, and BTC = 1,3,5-benzene tricarboxylate), one part of boron imidazolate ligands participate in the structural skeleton coordination, while another part of boron imidazolate ligands act as guest molecules that are located between adjacent nanotubes, which enhance the stability of the framework by the host-guest interaction and the pore space partition effects. It was found to be highly stable in air, water, organic solvents, and a wide pH range (pH 0-12). However, in the structure of BIF-135 ([Zn(BH(2-mim)₃)(CHTC)_1/3]; CHTC = 1,3,5-cyclohexanetricarboxylate), all boron imidazolate ligands participate in the structural skeleton coordination; there is no boron imidazolate guest molecule in the pores. The topology of BIF-135 is similar to that of BIF-134 by replacing BTC with CHTC and replacing Co with Zn. Furthermore, the obtained BIFs exhibited third-order nonlinear optical properties and potential optical limiting applications demonstrated by reverse saturable absorption.

Large breathing effect in ZIF-65(Zn) with expansion and contraction of the SOD cage

The flexibility and guest-responsive behavior of some metal-organic frameworks (MOFs) indicate their potential in the fields of sensors and molecular recognition. As a subfamily of MOFs, the flexible zeolitic imidazolate frameworks (ZIFs) typically feature a small displacive transition due to the rigid zeolite topology. Herein, an atypical reversible displacive transition (6.4 Å) is observed for the sodalite (SOD) cage in flexible ZIF-65(Zn), which represents an unusually large breathing effect compared to other ZIFs. ZIF-65(Zn) exhibits a stepwise II → III → I expansion between an unusual ellipsoidal SOD cage (8.6 Å × 15.9 Å for II) and a spherical SOD cage (15.0 Å for I). The breathing behavior of ZIF-65(Zn) varies depending on the nature of the guest molecules (polarity and shape). Computational simulations are employed to rationalize the differences in the breathing behavior depending on the structure of the ZIF-65(Zn) cage and the nature of the guest-associated host–guest and guest–guest interactions.

Flexible metal-organic frameworks have potential applications in the development of sensors and switching materials. Here, the authors report a large breathing effect in a zeolitic imidazolate framework upon guest adsorption.

Trinuclear Magnesium Imidazolate Borohydride Complex

A new type of hybrid compound, combining properties of MOFs and borohydrides, was synthesized solvothermally using Mg(BH₄)₂ and imidazole as precursors. Material in the form of acetonitrile solvate with formula [Mg₃{(Im)BH₂(Im)}₆(ImH)₆]·CH₃CN crystallizes in the space group R3̅, having the unit cell parameters a = 15.1942(2) Å and c = 28.3157(3) Å as determined by single crystal X-ray diffraction. The structure was further investigated by solid-state NMR and DFT quantum chemical calculations. The main feature of the structure, reported here for the first time, is a linear trinuclear complex, where octahedrally nitrogen-coordinated Mg²⁺ ions are bridged with {(Im)BH₂(Im)}^- units, forming inside voids of 4.6 Å in diameter between the magnesium ions. Polar intermolecular interactions hold the molecules in a dense rhombohedral stacking, where a disordered acetonitrile molecule plays a cohesive role. The compound is stable in air and upon heating to about 160 °C. Using an alternative synthesis method from an imidazole melt, an imidazole solvate with the formula [Mg₃{(Im)BH₂(Im)}₆(ImH)₆]·ImH and a very similar crystal structure to acetonitrile solvate was prepared. It is stable up to 220 °C. Upon further heating, it transformed into a layered structure with the formula Mg(Im₃BH)₂, space group P3̅1c, and unit cell parameters a = 8.7338(9) Å and c = 17.621(2) Å determined by synchrotron powder diffraction. Besides its structural novelty, two types of potentially reactive hydrogens, bonded to boron and nitrogen in the same molecule, make the material highly interesting for future investigations in the fields of energy storage applications.

Efficient neutron radiation shielding by boron-lithium imidazolate frameworks

Radiation protective materials are widely applied to avoid occupational hazards from either particle emissions or high-energy electromagnetic waves. Herein, we present a boron imidazolate framework (BIF) as a novel neutron shielding additive with high neutron capture cross-section elements B/Li and H. The BIF1-based epoxy resin matrix (Ep-BIF1) possesses high thermal stability and excellent resistance capacity. The neutron radiation shielding property was characterized using an Am-Be source, in which the thermal neutron shielding efficiency of Ep-BIF1 is notably higher than that of Ep-B₄C with equal boron concentration, showing potential applications as an advanced efficient neutron radiation shielding composite.

Induction of Chirality in Boron Imidazolate Frameworks: The Structure-Directing Effects of Substituents

By enhancing steric hindrance of substituents on the imidazole ring, the fan-shaped molecule of a tridentate boron imidazolate ligand (KBH(2-ipim)₃, 2-ipim = 2-isopropylimidazolate) with racemic chirality was obtained. Then, seven novel boron imidazolate frameworks (BIFs) were prepared by mixing KBH(2-ipim)₃ ligands with various derivatives of benzene carboxylic acid under solvothermal conditions. All of these seven materials contain a ladder-like zinc-boron-imidazolate chain as a basic building block, and the ligand BH(2-ipim)₃^- exists in the same handedness in one chain. The structural variations are associated with the position of substituents of the auxiliary ligand. Of particular interest is the spontaneous resolution of BH(2-ipim)₃^- ligands into two independent enantiomorphous homochiral structures, BIF-131-S and BIF-131-R, which contain both a chiral chain and an absolute helix embedded in the nets.

Hydroamination of Phenylacetylene with Aniline over Gold Nanoparticles Embedded in the Boron Imidazolate Framework BIF-66 and Zeolitic Imidazolate Framework ZIF-67

The hydroamination of alkynes is an atom-economy process in the organic synthesis for the C-N bond formation, thereby allowing the production of fine chemicals and intermediates. However, direct interaction between alkynes and amines is complicated due to the electron enrichment of both compounds. Therefore, efficient hydroamination catalysts, especially heterogeneous ones, are in great demand. This work aimed at the development of novel heterogeneous catalysts based on zeolite-like metal-organic frameworks for phenylacetylene hydroamination. The sodalite (SOD) type zeolitic imidazolate framework ZIF-67 (Co(meim)₂, meim = 2-methylimidazolate) and boron imidazolate framework BIF-66 ({Co[B(im)₄]₂}_n, im = imidazolate) were studied as the carriers for the gold nanoparticles (Au-NPs). Au-NPs were embedded in the ZIF-67 and BIF-66 matrices by incipient wetness impregnation. Au@ZIF-67 and Au@BIF-66 hybrids were studied for the first time in the liquid phase hydroamination of phenylacetylene with aniline in an air atmosphere and have shown high activity and selectivity in respect to imine in this process. The pronounced impact of the nature of the metal-organic carrier, Au source, and reducing agent on the catalytic performance of the synthesized nanomaterials was found. To the best of our knowledge, it is the first example of using the zeolitic imidazolate framework and boron-imidazolate framework as the components of the gold-containing catalytic systems for the alkyne hydroamination.

Application of Porous Materials for CO2 Reutilization: A Review

CO2 reutilization processes contribute to the mitigation of CO2 as a potent greenhouse gas (GHG) through reusing and converting it into economically valuable chemical products including methanol, dimethyl ether, and methane. Solar thermochemical conversion and photochemical and electrochemical CO2 reduction processes are emerging technologies in which solar energy is utilized to provide the energy required for the endothermic dissociation of CO2. Owing to the surface-dependent nature of these technologies, their performance is significantly reliant on the solid reactant/catalyst accessible surface area. Solid porous structures either entirely made from the catalyst or used as a support for coating the catalyst/solid reactants can increase the number of active reaction sites and, thus, the kinetics of CO2 reutilization reactions. This paper reviews the principles and application of porous materials for CO2 reutilization pathways in solar thermochemical, photochemical, and electrochemical reduction technologies. Then, the state of the development of each technology is critically reviewed and evaluated with the focus on the use of porous materials. Finally, the research needs and challenges are presented to further advance the implementation of porous materials in the CO2 reutilization processes and the commercialization of the aforementioned technologies.

Glassy behaviour of mechanically amorphised ZIF-62 isomorphs

Zeolitic imidazolate frameworks (ZIFs) can be melt-quenched to form glasses. Here, we present an alternative route to glassy ZIFs via mechanically induced amorphisation. This approach allows various glassy ZIFs to be produced in under 30 minutes at room temperature, without the need for melt-quenching.

Chiral induction in boron imidazolate frameworks: the construction of cage-based absolute helices

Two cage-based boron imidazolate helices were prepared in achiral reaction systems by mixing a C3 symmetric rigid ligand, KBH(bim)3, and a long flexible dicarboxylic acid ligand. The presence of an appropriate chiral inducer can control the helical orientation of bulk samples, which further acts on the enantioselective separation of racemic 1-phenylethanol.

Recent progress and perspectives on the structural design on metal-organic zeolite (MOZ) frameworks

As a typical group of coordination polymers, metal-organic zeolite (MOZs) frameworks inherit the topological and structural advantages of inorganic zeolites and display great application potential in many areas, including gas adsorption/separation, catalysis, luminescence and chemical sensing. In this review, we outline the recent progress in the synthesis, functionalization and application of metal-organic zeolite frameworks, mainly focusing on the basic structural design principle and synthesis strategy on 4-connect inorganic nodes and 2-connect organic linkers. Employing different valent metals, small inorganic TO₄^2- units and high-nuclear clusters as 4-connect nodes, we derived multi-types of MOZs with a modified framework charge, improved stability and enhanced photo-/eletrocatalytic activity. Besides, the selection, functionalization and defect-engineering on the 2-connect ligands generated different topological and functional MOZs. Finally, the future trends and some perspectives in this area are outlined.

Synthesis of a new ATN-type zeolitic imidazolate framework through cooperative effects of N,N-dipropylformamide and n-butylamine

ATN-[Zn(Im)₂] is the first known example of a ZIF exhibiting a zeolitic ATN topology, which was prepared using the cooperative effects of N,N-dipropylformamide and n-butylamine.

Synthesis of Supramolecular Boron Imidazolate Frameworks for CO2 Photoreduction

Presented here are two novel porous supramolecular boron imidazolate frameworks (BIF-106 and BIF-107), which are stabilized through relatively weak interactions between two-dimensional boron imidazolate layers. Moreover, BIF-107 exhibits efficient CO₂ photoreduction to CO with a remarkable rate of 1186.0 μmol·g^-1·h^-1 under visible-light irradiation.

Cobalt-Based Metal-Organic Frameworks and Their Derivatives for Hydrogen Evolution Reaction

Hydrogen has been considered as a promising alternative energy to replace fossil fuels. Electrochemical water splitting, as a green and renewable method for hydrogen production, has been drawing more and more attention. In order to improve hydrogen production efficiency and lower energy consumption, efficient catalysts are required to drive the hydrogen evolution reaction (HER). Cobalt (Co)-based metal-organic frameworks (MOFs) are porous materials with tunable structure, adjustable pores and large specific surface areas, which has attracted great attention in the field of electrocatalysis. In this review, we focus on the recent progress of Co-based metal-organic frameworks and their derivatives, including their compositions, morphologies, architectures and electrochemical performances. The challenges and development prospects related to Co-based metal-organic frameworks as HER electrocatalysts are also discussed, which might provide some insight in electrochemical water splitting for future development.

The highly selective detecting of antibiotics and support of noble metal catalysts by a multifunctional Eu-MOF

Designing novel multifunctional rare-earth metal-organic frameworks (MOFs) has attracted intensive attention. In particular, employing such materials for sensing or catalytic reactions is still very challenging. Here, a new 3D porous Eu(iii)-MOF, [Eu(cppa)(OH)]·xS (denoted as CTGU-19, S = solvent molecule, CTGU = China Three Gorges University), was synthesized by using 5-(4-carboxyphenyl)picolinic acid (H2cppa) as an organic ligand, and it shows a 3D (3,12)-connected topological net with the point symbol (420·628·818)(43)4, constructed from cubane-shaped tetranuclear europium building units. Interestingly, CTGU-19 can be used as a highly sensitive luminescent sensor to identify ornidazole (ODZ) and nitrofurantoin (NFT) at different excitation wavelengths. This result represents the first example of a lanthanide-metal-organic-framework (Eu-MOF) that can be employed as a discriminating fluorescent probe to recognize ODZ and NFT at different excitation wavelengths. Furthermore, after loading CTGU-19 with Ag and/or Au nanoparticles, the composites exhibit efficient catalytic performance for reducing 2-/3-/4-nitrophenols (2-/3-/4-NP), in which the unit mass reduction rate constants of Ag0.8Au0.2@CTGU-19 for 2-NP, 3-NP, and 4-NP reach 68.8, 53.80, and 52.34 s-1 g-1, respectively.

A novel core-shell upconversion nanoparticles@zirconium-based metal organic framework fluorescent nanoprobe for efficient continuous detection of trace methylene blue and ferrous ions

Herein, we have synthesized Gd₂O₃:Yb,Er@UiO-66-NH₂ (UiO-66-NH₂ represent a zirconium-based metal organic framework [Zr₆O₄(OH)₄(ata)₁₂], ata: 2-aminoterephthalate) core-shell composites to develop an upconversion fluorescent nanoprobe for efficient detection of trace methylene blue (MB) and ferrous ions (Fe²⁺). Due to the fluorescence of the nanoprobe can be quenched by MB based on inner filter effect, but gradually recover when contact with ·OH, which is generated from the reaction between H₂O₂ and Fe²⁺, we have achieved the detection of Fe²⁺. The detection linear range is from 1.78 to 15.8 μM, and the limit of detection (LOD) is 0.071 μM. Besides, in this process, we also simultaneously realize the detection of MB. The linear range of MB turn-off detection is 0-42.6 μM, and the LOD is 0.41 μM. To our knowledge, no example of using upconversion fluorescence probe for continuous detection of trace MB and Fe²⁺ has been reported for now, and test results are superior compared with most reported Fe²⁺ probes. Moreover, the combinations of upconversion nanoparticles (UCNPs) and the metal-organic frameworks (MOFs) have enhanced the selectivity and sensitivity of the probe towards MB and Fe²⁺. Therefore, we believe the designed upconversion fluorescent nanoprobe is a promising efficient tool in detecting MB and diagnose Fe²⁺ related diseases in the future.

Charge-Separated and Lewis Paired Metal-Organic Framework for Anion Exchange and CO2 Chemical Fixation

Charge-separated metal-organic frameworks (MOFs) are a unique class of MOFs that can possess added properties originating from the exposed ionic species. A new charge-separated MOF, namely, UNM-6 synthesized from a tetrahedral borate ligand and Co²⁺ cation is reported herein. UNM-6 crystalizes into the highly symmetric P43n space group with fourfold interpenetration, despite the stoichiometric imbalance between the B and Co atoms, which also leads to loosely bound NO₃ ^- anions within the crystal structure. These NO₃ ^- ions can be quantitatively exchanged with various other anions, leading to Lewis acid (Co²⁺ ) and Lewis base (anions) pairs within the pores and potentially cooperative catalytic activities. For example, UNM-6-Br, the MOF after anion exchange with Br^- anions, displays high catalytic activity and stability in reactions of CO₂ chemical fixation into cyclic carbonates.

Temperature Feedback-Controlled Photothermal/Photodynamic/Chemodynamic Combination Cancer Therapy Based on NaGdF4 :Er,Yb@NaGdF4 :Nd@Cu-BIF Nanoassemblies

The intelligent design of multifunctional nanoplatforms is critical for cancer therapy. Herein, NaGdF₄ :Er,Yb@NaGdF₄ :Nd@Cu(II) boron-imidazolate frameworks (denoted as CSNPs@Cu-BIF) nanoassemblies are designed and fabricated. Upon a single 808 nm laser irradiation, the nanoassemblies not only show the outstanding photothermal conversion capacity (η = 41.7%) but also generate cytotoxic reactive oxygen species through an in situ Fenton-like reaction and fluorescence resonance energy transfer. Importantly, the nanoassemblies simultaneously introduce remarkable antitumor efficacy via photothermal/photodynamic/chemodynamic combination therapy both in vitro and in vivo. To improve the therapeutic effect of solid tumor ablation, it is highly desirable to monitor the treatment process in real-time. Multiclinical imaging modalities of ultrasonography are employed to systematically investigate the ablation mechanism of solid tumors in vivo. Furthermore, the significant difference between the eigen temperature of CSNPs@Cu-BIF nanoassemblies obtained by the temperature-sensitive emission bands signal changes and the apparent temperature recorded by the thermal imaging camera is 14.55 K at equilibrium. This current work therefore supplies an alternative strategy in temperature feedback-controlled accurate cancer therapy.

Solid phase extraction-based magnetic carbon nitride/metal organic framework composite with high performance liquid chromatography for the determination of tyrosine kinase inhibitors in urine samples

In this study, a novel solid phase extraction method was constructed to detect three tyrosine kinase inhibitors (TKIs) in urine with a high-performance liquid chromatography-diode array detector. The sorbent MCN/BIF-20 was constructed by magnetic g-C₃N₄ (MCN) and boron imidazole framework-20 (BIF-20) and was characterized by multiple techniques. The experimental results of the adsorption isotherm and adsorption kinetics indicated that the composites had good adsorption of TKIs (148.33 mg g^-1, 283.25 mg g^-1, 188.17 mg g^-1). The reason for the good adsorption property of the complex material was revealed by comparison with each single material. The analytical method was built by a single factor experiment, and was evaluated as a suitable method to detect TKIs in urine by its good accuracy (90.35-98.69%), precision (<3.9%), appropriate detection limits (2.2-3.4 ng mL^-1), and linear ranges (12.5-500 ng mL^-1) with convenient determination coefficients (>0.9997). The performance of the MCN/BIF-20 composite did not decrease dramatically in 3 cycles. These analytical results demonstrated that g-C₃N₄ and BIFs had a bright prospect in sample pretreatment, and the proposed approach based on MCN/BIF-20 was applicable for analysis of TKIs in urine.

Single-Atom Catalysts across the Periodic Table

Isolated atoms featuring unique reactivity are at the heart of enzymatic and homogeneous catalysts. In contrast, although the concept has long existed, single-atom heterogeneous catalysts (SACs) have only recently gained prominence. Host materials have similar functions to ligands in homogeneous catalysts, determining the stability, local environment, and electronic properties of isolated atoms and thus providing a platform for tailoring heterogeneous catalysts for targeted applications. Within just a decade, we have witnessed many examples of SACs both disrupting diverse fields of heterogeneous catalysis with their distinctive reactivity and substantially enriching our understanding of molecular processes on surfaces. To date, the term SAC mostly refers to late transition metal-based systems, but numerous examples exist in which isolated atoms of other elements play key catalytic roles. This review provides a compositional encyclopedia of SACs, celebrating the 10th anniversary of the introduction of this term. By defining single-atom catalysis in the broadest sense, we explore the full elemental diversity, joining different areas across the whole periodic table, and discussing historical milestones and recent developments. In particular, we examine the coordination structures and associated properties accessed through distinct single-atom-host combinations and relate them to their main applications in thermo-, electro-, and photocatalysis, revealing trends in element-specific evolution, host design, and uses. Finally, we highlight frontiers in the field, including multimetallic SACs, atom proximity control, and possible applications for multistep and cascade reactions, identifying challenges, and propose directions for future development in this flourishing field.

Structural Tuning and Pore Modulation of Three Cu(II)-Organic Frameworks: Enhancement of Stability and Functionality

Through use of an irregular pentacarboxylate ligand, 2,2'-(pyridine-2,6-diyl)diterephthalic acid (H₄L), two Cu(II)-based metal-organic frameworks, {[(Me₂NH₂)_0.5][Cu_0.75(L)_0.5(DMA)_0.375]·H₂O}_n (1) and {[Cu₄(L)₂(H₂O)₄]·4DMF·8H₂O}_n (2), have been synthesized. A structural analysis demonstrates that 1 is a 2D layer and 2 shows a 3D framework, which exhibit hopeful possibilities for the selective separations of C₂H₂/CH₄ and CO₂/CH₄. To enhance the adsorption properties, 5-amino-1H-tetrazole (HAT) has been introduced in the synthesis system, and a new framework, {[Cu₄(L)₂(ATZ)₂(H₂O)]·5DMF·5H₂O}_n (3), has been obtained. 3 is a 3D framework. Especially, 3 is constructed from multiple SBUs and displays an unusual (3,4,6)-connected topology. Furthermore, especially 3 performs better than 1 and 2 in terms of uptake capacity as well as adsorption selectivity, which might be ascribed to the more proper pore space of 3.

Zeolite-Like Boron Imidazolate Frameworks (BIFs): Synthesis and Application

This review is devoted to discussion of the latest advances in design and applications of boron imidazolate frameworks (BIFs) that are a particular sub-family of zeolite-like metal–organic frameworks family. A special emphasis is made on nanostructured hybrid materials based on BIF matrices and their modern applications, especially in environment remediation and energy conversion.

In-situ synthesis of metal nanoparticles@metal-organic frameworks: Highly effective catalytic performance and synergistic antimicrobial activity

M-NP@Zn-BIF (M-NP = Ag or Cu nanoparticle; Zn-BIF is a zinc-based boron imidazolate framework, Zn₂(BH(2-mim)₃)₂(obb); 2-mim = 2-methylimidazole; obb = 4,4'-oxybis(benzoate)) composites were successfully in-situ synthesized by utilizing the reducing ability of the BH bond contained in the Zn-BIF at room temperature without any additional chemical reduction reagents. These composites (225 μg/mL) exhibited excellent catalytic activity to convert 4-nitrophenol to 4-aminophenol in 2.5 min and 6 min with a conversion rate of 99.9 %, respectively. In addition, Ag@Zn-BIF (50 μg/mL) showed highly synergistic antibacterial activity against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) with a bactericidal rate of approximately 99.9 %. An antibacterial mechanism was proposed for the generation of intracellular reactive oxygen species (ROS) levels. Superoxide radicals (O^2-) and hydroxyl radicals (OH) formed during the antibacterial process were shown to accelerate the death of bacteria. They also exhibited highly photocatalytic activity for Rhodamine B (RhB). When the concentration of the composites is 1000 μg/mL, the photocatalytic efficiency of Ag@Zn-BIF and Cu@Zn-BIF increased by 31.62 and 18.13 times compared with Zn-BIF, respectively. All in all, this study developed a simple and versatile integrated platform for the removal of nitrophenols, organic dyes, and the effective inactivation of bacteria in water.

Synthesis and Photoelectric Properties of Metal-Organic Zeolites Built from TO4 and Organotin

Herein we report a novel strategy capable of generating a new class of metal-organic zeolite (MOZ) materials. When the MoO₄ or WO₄ tetrahedra are employed to assemble with triorganotin R₃Sn fragments, four 3D networks with the zeolite BCT topology and nonzeotype 4-connected topological net (such as lon and dia) have been generated. The photocurrent study results show that these materials have good photoelectric response and high photophysical stability.

Co (II) Boron Imidazolate Framework with Rigid Auxiliary Linkers for Stable Electrocatalytic Oxygen Evolution Reaction

Metal-organic frameworks (MOFs) have significant potential for practical application in catalysis. However, many MOFs are shown to be sensitive to aqueous solution. This severely limits application of MOFs in electrocatalytic operations for energy production and storage. Here, a Co (II) boron imidazolate framework CoB(im)4(ndc)0.5 (BIF-91, im = imidazolate, ndc = 2,6-naphthalenedicarboxylate) that is rationally designed and successfully tested for electrocatalytic application in strong alkaline (pH ≈ 14) solution is reported. In such a BIF system, the inherent carboxylate species segment large channel spaces into multiple domains in which each single channel is filled with ndc ligands through the effect of zeolite channel confinement. These ligands, with strong C-H···π interaction, act as a rigid auxiliary linker to significantly enhance the structural stability of the BIF-91 framework. Additionally, the π-conjugated effect in BIF-91 stabilizes dopant Fe (III) at the atomic scale to construct Fe-immobilized BIF-91 (Fe@BIF-91). Due to the synergistic effect between Fe (III) guest and Co (II) in the framework, the Fe@BIF-91 acts as an active and stable electrocatalyst for the oxygen evolution reaction in alkaline solution.

CdS nanosphere-decorated hollow polyhedral ZCO derived from a metal-organic framework (MOF) for effective photocatalytic water evolution

Semiconductor nanostructures have received considerable attention in the field of photocatalytic hydrogen evolution. However, eco-friendly, high efficiency, and low-cost semiconductor materials are still desired. In consideration of this, herein, we design a new and economic noble-metal-free CdS/Zn_xCo_3-xO₄ (CdS/ZCO) nanohybrid photocatalyst using a metal-organic framework (MOF) template, which is a framework structure composed of organic ligands and metal ion nodes with different numbers of connections. The as-prepared CdS/ZCO composites with a large specific surface area and porous hollow structure exhibit remarkable catalytic activity and high stability for hydrogen generation. The hydrogen evolution rate is about 3978.6 μmol g^-1 h^-1 with lactic acid as the sacrificial agent when the optimized amount of CdS nanoparticles (30 wt%) is decorated on the ZCO frame, and the production efficiency of H₂ for CdS/ZCO is 4 times higher than that for CdS nanospheres or CdS/Co₃O₄. The significantly enhanced photocatalytic activity of CdS/ZCO is attributed to the efficient charge separation and transfer between the phase boundary of CdS and ZCO. In addition, the composites exhibit better hydrogen production in lactic acid than in methanol, and the remarkable catalytic activity and high stability of the CdS/ZCO composites for hydrogen evolution indicate that MOF-based composite materials have potential application prospects in energy conversion.

Design and synthesis of multifunctional metal-organic zeolites

Metal-organic zeolites (MOZs) are an important branch of metal-organic frameworks (MOFs) and combine the advantages of zeolites and MOFs, such as high surface area and porosity as well as the exceptional stability of zeolites, which would have a significant impact on catalysis chemistry, inorganic chemistry, coordination chemistry, materials science and other areas. In this review, we focus on the recent advances in MOZs with a brief outline of the most prominent examples. In particular, we highlight the basic principles of the design and synthesis approaches toward the construction of MOZs. Obeying the principle of charge matching, tuning tetrahedral metal centers, using enlarged tetrahedral building units as clusters, introducing functional groups into ligands, and combining traditional inorganic TO₄ sites in MOZs enable the final materials with diverse topological structures to exhibit superior performance for various applications, such as gas sorption/separation, catalysis, enantio-selectivity, luminescence, etc.

Construction of unprecedented pillar-layered metal organic frameworks via a dual-ligand strategy for dye degradation

Presented here are two new pillar-layered MOFs based on different metal–carboxylate SBUs employed by mixing D-H₂Cam and OH-bim ligands. The Zn/Co mixed compound 2 exhibits an adjustable Zn/Co ratio, which reversibly results in an adjustable photocatalytical property of dye degradation.

Synthesis of zeolitic tetrazolate-imidazolate frameworks (ZTIFs) in ethylene glycol

Ethylene glycol (EG) as a universal solvent is used to reproducibly synthesize zeolitic tetrazolate imidazolate frameworks (ZTIF-11 to 13) in high yields, among which the frl-type ZTIF-11 shows high chemical stability and porosity as well as remarkable CO₂ gas separation.

Light-enhanced acid catalysis over a metal–organic framework

A sulfonate group-functionalized metal–organic framework exhibits unprecedented light-enhanced catalytic activity, even higher than H₂SO₄, and excellent recyclability toward acid-engaged reactions under light irradiation.

Thermally Stable Metal-Organic Framework-Templated Synthesis of Hierarchically Porous Metal Sulfides: Enhanced Photocatalytic Hydrogen Production

Porous nanostructured materials are demonstrated to be very promising in catalysis due to their well accessible active sites. Thermally stable metal-organic frameworks (MOFs) as hard templates are successfully utilized to afford porous metal oxides and subsequently metal sulfides by a nanocasting method. The resultant metal oxides/sulfides show considerable Brunauer-Emmett-Teller (BET) surface areas, by partially inheriting the pore character of MOF templates. Preliminary investigation on the obtained hierarchically porous CdS for water splitting, as a proof of concept, demonstrates its much higher activity than both corresponding bulk and nanosized counterparts, under visible light irradiation. Given the structural diversity and tailorability of MOFs, such synthetic approach may open an avenue to the synthesis of advanced porous materials for functional applications.