Stable Metal-organic Framework Research Articles

T-type capture site within highly stable bicarbazole-based metal–organic framework for C2H2 purification from CO2 and CH4

It is challenging to achieve high-purity acetylene (C2H2) from the methylene (CH4) and carbon dioxide (CO2), due to their similar molecular structure and physical properties. Adsorption utilized porous materials, such as metal–organic frameworks (MOFs), has been considered as cost- and energy-efficient technology to separate acetylene mixtures. Herein, we reported a highly stable MOF, [Zn6L4(Me2NH2+)4‧3H2O] (named FJU-83), featuring T-shaped functional capture sites explored for acetylene capture and separation. In addition, FJU-83a exhibits not only a high C2H2 uptake capacity of 122.9 cm3/g at 273 K, 1 bar, but also good C2H2/CH4 and C2H2/CO2 selectivity of 24 and 2.9 under moderate temperature and 1 bar, respectively. The high separation efficiency of the C2H2/CH4 and C2H2/CO2 are validated by dynamic fixed bed breakthrough experiments. The single crystal X-ray diffraction studies and Hirshfeld surface analysis revealed that T-type aromatic sites of FJU-83a can separate C2H2 from CH4 and CO2 through multiple C-H∙∙∙π and π∙∙∙π interactions.

Conductive Lanthanide Metal-Organic Frameworks with Exceptionally High Stability.

Electrically conductive metal-organic frameworks (MOFs) have been extensively studied for their potential uses in energy-related technologies and sensors. However, achieving that goal requires MOFs to be highly stable and maintain their conductivity under practical operating conditions with varying solution environments and temperatures. Herein, we have designed and synthesized a new series of {[Ln4(μ4-O)(μ3-OH)3(INA)3(GA)3](CF3SO3)(H2O)6}n (denoted as Ln4-MOFs, Ln = Gd, Tm, and Lu, INA = isonicotinic acid, GA = glycolic acid) single crystals, where electrons are found to transport along the π-π stacked aromatic carbon rings in the crystals. The Ln4-MOFs show remarkable stability, with minimal changes in conductivity under varying solution pH (1-12), temperature (373 K), and electric field as high as 800 000 V/m. This stability is achieved through the formation of strong coordination bonds between high-valent Ln(III) ions and rigid carboxylic linkers as well as hydrogen bonds that enhance the robustness of the electron transport path. The demonstrated lanthanide MOFs pave the way for the design of stable and conductive MOFs.

Design and structural characteristics of conducting polymer-metal organic framework composites for energy storage devices

The popularity of portable gadgets has increased the supply for energy storage systems with significant power and energy densities Redox-active conducting polymers (CPs) have mechanical qualities similar to polymers and electrical conductivity properties similar to metals. Unfortunately, the volume changes that occur throughout the charge and discharge procedures cause them to function poorly. An efficient method to attain high performance is to combine CPs with metal-organic frameworks (MOF) to create composites. Despite MOFs' extraordinary interior surface areas and adaptable pore structures, they have poor stability, polymers can improve MOF stability and improve other crucial characteristics like electrical conductivity. The combination of these two different components can result in a variety of desired features that are not always attained by these components individually. The recent research on conducting polymer-based metal-organic framework (CP/MOF) composites for energy storage applications is thoroughly surveyed in this review paper. This review focuses on various CP/MOF-based fuel cells, batteries and supercapacitors, pertinent fabrication techniques, and important design principles.

Highly Efficient Propyne/Propylene Separation in a "Flexible-Robust" and Hydrolytically Stable Cu(II)-MOF.

Propyne/propylene separation is important in the petrochemical industry but challenging due to their similar physical properties and close molecular sizes. Metal-organic frameworks (MOFs) are a class of promising adsorbents for light hydrocarbon separations. Among them, the so-called "flexible-robust" MOFs combine the advantages of flexibility and rigidity in structure and could show enhanced gas separation selectivity as well as improved gas uptake at low pressure. Interpenetrated MOFs offer a platform to explore the "flexible-robust" feature of MOFs based on their subnetwork displacement in the process of gas adsorption. Herein, we present two hydrolytically stable MOFs (BUT-308 and BUT-309) with interpenetrated structures and fascinating propyne/propylene separation performance. BUT-308 is composed of interpenetrated 2D Cu(BDC-NH2)BPB layers (H2BDC-NH2 = 2-aminobenzene-1,4-dicarboxylic acid; BPB = 1,4-bis(4-pyridyl)benzene), while BUT-309 consists of twofold interpenetrated 3D pillared-layer Cu2(BDC-NH2)2(BPB-CF3) nets (BPB-CF3 = 2-trifluoromethyl-1,4-bis(4-pyridyl)benzene). Gas adsorption measurements showed that BUT-309 was a "flexible-robust" adsorbent with multistep adsorption isotherms for C3H4 rather than C3H6 at a wide temperature range. The guest-dependent pore-opening behavior endows BUT-309 with high potential in the C3H4/C3H6 separation. The C3H4 adsorption measurements of BUT-309 at 273-323 K showed that the lowering of the temperature induced the pore-opening action at lower pressure. Column breakthrough experiments further confirmed the capability of BUT-309 for the efficient removal of C3H4 from a C3H4/C3H6 binary gas, and the C3H6 processing capacity at 273 K (15.7 cm3 g-1) was higher than that at 298 K (35.2 cm3 g-1). This work shows a rare example of "flexible-robust" MOFs and demonstrated its high potential for C3H4/C3H6 separation.

Pore engineering in cost-effective and stable Al-MOFs for efficient capture of the greenhouse gas SF6

The capture and separation of the greenhouse gas sulfur hexafluoride (SF6) from nitrogen (N2) holds significant potential for mitigating the greenhouse effect and yielding economic advantages for the semiconductor industry. In this study, a pair of isoreticular cost-effective and stable metal–organic frameworks (MOFs) with slightly different pore environments (CAU-10-H and CAU-10-Py) were prepared at >10 g scale for SF6/N2 separation. CAU-10-Py exhibited a remarkable improvement in SF6 uptake capacity at both low pressure (1.13 mmol/g at 0.1 bar and 298 K, compared to 0.68 mmol/g) and elevated pressure (2.11 mmol/g at 1 bar and 278 K, compared to 1.07 mmol/g). The ideal adsorbed solution theory (IAST) selectivity of SF6/N2 (10/90) was found to be 204 for CAU-10-Py and 123 for CAU-10-H. These enhanced capacities and selectivity endow CAU-10-Py a highly promising candidate for SF6 capture. Single crystal structural analysis, 77 K N2 adsorption data and theoretical calculations indicated that the substitution of benzene by pyridine slightly expand the pore diameter, facilitating more efficient accommodation of SF6 within the channel pores. The SF6 molecule is adsorbed around four benzene rings in CAU-10-H but trapped by two pyridine rings in CAU-10-py, resulting in one fold increase in adsorption capacity. Intriguingly, time-dependant adsorption experiments revealed that CAU-10-Py exhibited a higher SF6 adsorption rate and a lower N2 adsorption rate compared to CAU-10-H, further highlighting the benefit of CAU-10-Py for SF6/N2 separation. Dynamic breakthrough experiments conducted under simulated working conditions further confirmed the outstanding SF6/N2 separation performance of CAU-10-Py. Considering its excellent regeneration ability and cycling performance, this cost-effective and easily scalable MOF demonstrates great promise for SF6/N2 separation.

Toward High-Performance Metal-Organic-Framework-Based Quasi-Solid-State Electrolytes: Tunable Structures and Electrochemical Properties.

Metal-organic frameworks (MOFs) have been reported as promising materials for electrochemical applications owing to their tunable porous structures and ion-sieving capability. However, it remains challenging to rationally design MOF-based electrolytes for high-energy lithium batteries. In this work, by combining advanced characterization and modeling tools, a series of nanocrystalline MOFs is designed, and the effects of pore apertures and open metal sites on ion-transport properties and electrochemical stability of MOF quasi-solid-state electrolytes are systematically studied. It isdemonstrated that MOFs with non-redox-active metal centers canlead to a much wider electrochemical stability window than those with redox-active centers. Furthermore, the pore aperture of MOFs is found to be a dominating factor that determines the uptake of lithium salt and thus ionic conductivity. The ab initio molecular dynamics simulations further demonstrate that open metal sites of MOFs can facilitate the dissociation of lithium salt and immobilize anions via Lewis acid-base interaction, leading to good lithium-ion mobility and high transference number. The MOF quasi-solid-state electrolyte demonstrates great battery performance with commercial LiFePO4 and LiCoO2 cathodes at 30°C. This work provides new insights into structure-property relationships between tunable structure and electrochemical properties of MOFs that can lead to the development of advanced quasi-solid-state electrolytes for high-energy lithium batteries.

Construction of 3D flower-like SnS particles anchored Ni-metal-organic framework composite: A novel positive electrode material for high-performance asymmetric supercapacitors

Metal-organic frameworks (MOFs) have gains particular consideration as electrode material in supercapacitors owing to their porous nature, tunable structure, and occurrence of many active sites. However, some pristine MOFs' poor electrical conductivity and stability confine their potential application in supercapacitors. In this work, a new type of Nickel-MOF-based tin sulfide composite (Ni-MOF/SnS) is prepared using the simple hydrothermal route and studied its applicability in supercapacitors. The physicochemical characterizations of the as-prepared Ni-MOF/SnS composite confirm the perfect synthesis and formation of porous 3Dimensional (3D) flower-like SnS particles anchored Ni-MOF hexagonal rods-like morphology. The existing porous structure and SnS particles in the Ni-MOF/SnS composite deliver many active sites to perform the electrochemical reactions, achieving an excellent specific capacity value of 1440 C/g at 1 A/g. Also, Ni-MOF/SnS composite electrode maintains 95 % of its specific capacity value up to 8000 charge-discharge cycles at 3 A/g. Furthermore, the as-fabricated Ni-MOF/SnS//Activated carbon asymmetric device delivers the specific capacity of 228 F/g at 1 A/g, revealing a high energy and power density of 81.06 Wh/kg and 1823.8 W/kg, respectively. These findings demonstrate that the Ni-MOF/SnS composite represents a suitable electrode material for the next generation of supercapacitors.

Study on the essential features for MOFs to reversible adsorption of H2S at room temperature

Metal-organic frameworks (MOFs) have been extensively studied for hydrogen sulfide (H2S) capture. However, reversible adsorption of H2S by MOFs materials, which allow the adsorbents to be repeatedly used, remains challenging. To get a rational insight into the reversible H2S adsorption on MOFs, eight MOFs with different features were selected as representatives, and their behaviors of adsorption and desorption for H2S in three cycles were investigated in a fixed-bed reactor. X-ray diffraction and nitrogen adsorption-desorption characterization were used to confirm the reversibility based on the alterations in MOFs’ physical and chemical properties before and after H2S adsorption. The results indicated that only UiO-66, MOF-801, and Mg-MOF-74 exhibited reversibility among these selected MOFs. Nevertheless, their highest H2S capacity is only 3.81 mg/g, far away from the practical application. Calculation results of adsorption sites, the density of states, adsorption distance, and the heat of adsorption show that a weak interaction between MOFs and H2S, which is afforded by metal centers or/and organic ligands, is needed for reversible adsorption. However, it is difficult to get a satisfactory H2S removal capacity in such a situation. Introducing new adsorption sites into structurally stable MOFs is considered an efficient strategy for increasing their reversible adsorption capacity.

Computational Discovery of Stable Metal-Organic Frameworks for Methane-to-Methanol Catalysis.

The challenge of direct partial oxidation of methane to methanol has motivated the targeted search of metal-organic frameworks (MOFs) as a promising class of materials for this transformation because of their site-isolated metals with tunable ligand environments. Thousands of MOFs have been synthesized, yet relatively few have been screened for their promise in methane conversion. We developed a high-throughput virtual screening workflow that identifies MOFs from a diverse space of experimental MOFs that have not been studied for catalysis, yet are thermally stable, synthesizable, and have promising unsaturated metal sites for C-H activation via a terminal metal-oxo species. We carried out density functional theory calculations of the radical rebound mechanism for methane-to-methanol conversion on models of the secondary building units (SBUs) from 87 selected MOFs. While we showed that oxo formation favorability decreases with increasing 3d filling, consistent with prior work, previously observed scaling relations between oxo formation and hydrogen atom transfer (HAT) are disrupted by the greater diversity in our MOF set. Accordingly, we focused on Mn MOFs, which favor oxo intermediates without disfavoring HAT or leading to high methanol release energies─a key feature for methane hydroxylation activity. We identified three Mn MOFs comprising unsaturated Mn centers bound to weak-field carboxylate ligands in planar or bent geometries with promising methane-to-methanol kinetics and thermodynamics. The energetic spans of these MOFs are indicative of promising turnover frequencies for methane to methanol that warrant further experimental catalytic studies.

MOF-Based Solid-State Proton Conductors Obtained by Intertwining Protic Ionic Liquid Polymers with MIL-101.

Solid-state proton conductors based on the use of metal-organic framework (MOF) materials as proton exchange membranes are being investigated as alternatives to the current state of the art. This study reports a new family of proton conductors based on MIL-101 and protic ionic liquid polymers (PILPs) containing different anions. By first installing protic ionic liquid (PIL) monomers inside the hierarchical pores of a highly stable MOF, MIL-101, then carrying out polymerization in situ, a series of PILP@MIL-101 composites was synthesized. The resulting PILP@MIL-101 composites not only maintain the nanoporous cavities and water stability of MIL-101, but the intertwined PILPs provide a number of opportunities for much-improved proton transport compared to MIL-101. The PILP@MIL-101 composite with HSO4 - anions shows superprotonic conductivity (6.3×10-2 Scm-1 ) at 85°C and 98% relative humidity. The mechanism of proton conduction is proposed. In addition, the structures of the PIL monomers were determined by single crystal X-ray analysis, which reveals many strong hydrogen bonding interactions with O/NH···O distances below 2.6Å.

Sulfonate-Grafted Metal–Organic Framework─A Porous Alternative to Nafion for Electrochemical Sensors

Nafion, a polymer containing negatively charged sulfonate groups, is commonly used as a thin film cast on the electrode to adjust the selectivity of complicated electrochemical reactions involving charged reactants or analytes in the electrochemical sensing and electrolytic systems. Herein, a highly porous and chemically stable metal–organic framework (MOF) with enriched sulfonate groups in its pores is synthesized by performing the postsynthetic immobilization of the sulfonate-based ligand within a zirconium-based MOF, MOF-808, and the resulting sulfonate-grafted MOF (SO3-MOF-808) is proposed as a “porous Nafion”─an appealing alternative to the conventional Nafion coating for modulating the selectivity of electrochemical reactions. As a demonstration, the electrochemical sensing of dopamine (DA), which usually suffers from interference caused by the oxidation of the coexisting negatively charged ascorbic acid (AA) and uric acid (UA), is implemented. With the use of the SO3-MOF-808 thin film deposited on the active electrode surface, both the current signal for DA oxidation and the selectivity toward the oxidation of DA against those of AA and UA remarkably outperform those achieved by the Nafion thin film with an optimized film thickness. Findings here suggest the new role of such sulfonate-grafted MOFs as an advanced alternative to Nafion in a range of electrochemical sensing systems and other complicated electrochemical reactions.

Deployment of Superhydrophilic and Super-antifouling Cr-soc-MOF-1-Based Membrane for Ultrafast Separation of Stabilized Oil-in-Water Emulsions.

In spite of massive progress in oil-water separation, attributable to the use of advanced materials, the separation process faces challenges such as low permeance and fouling problems. Therefore, superwettable materials used in several fields are considered potential candidates for oily wastewater treatment. Metal-organic frameworks (MOFs) are receiving more and more interest in various separation applications due to their wide potential applications. Nevertheless, MOFs have been rarely explored for separating stabilized oil-in-water emulsions due to the difficulty in finding highly hydrolytic stable MOF candidates for this application. Furthermore, oil can clog water-stable materials owing to its high density, causing the degradation of MOF particles. As a result, there is a need to develop better MOF materials that can fulfill these requirements. Herein, we have explored Cr-soc-MOF-1 as a candidate for this application and deployed it as a membrane, which exhibited superhydrophilicity and underwater superoleophobicity for separating stabilized oil-in-water emulsions. The Cr-soc-MOF-1 membranes were synthesized by assembling the as-prepared MOF particles on a mixed cellulose ester substrate using a vacuum-assisted self-assembly technique. The Cr-soc-MOF-1 membrane exhibited ultrahigh water permeance (7465.9 L·m-2·h-1·bar-1), very high oil rejection (99.9%), and excellent anti-oil-fouling properties. The Cr-soc-MOF-1 membranes also exhibited excellent recyclability over 10 continuous separation cycles. Further, they exhibited an outstanding performance in separating various surfactant-stabilized oil-in-water emulsions. Thus, the Cr-soc-MOF-1 membranes exhibit a high potential in treating oily wastewater.

Immobilization of the Polar Group into an Ultramicroporous Metal-Organic Framework Enabling Benchmark Inverse Selective CO2/C2H2 Separation with Record C2H2 Production.

One-step harvest of high-purity light hydrocarbons without the desorption process represents an advanced and highly efficient strategy for the purification of target substances. The separation and purification of acetylene (C2H2) from carbon dioxide (CO2) by CO2-selective adsorbents are urgently demanded yet are very challenging owing to their similar physicochemical properties. Here, we employ the pore chemistry strategy to adjust the pore environment by immobilizing polar groups into an ultramicroporous metal-organic framework (MOF), achieving one-step manufacture of high-purity C2H2 from CO2/C2H2 mixtures. Embedding methyl groups into prototype stable MOF (Zn-ox-trz) not only changes the pore environment but also improves the discrimination of guest molecules. The methyl-functionalized Zn-ox-mtz thus exhibits the benchmark reverse CO2/C2H2 uptake ratio of 12.6 (123.32/9.79 cm3 cm-3) and an exceptionally high equimolar CO2/C2H2 selectivity of 1064.9 at ambient conditions. Molecular simulations reveal that the synergetic effect of pore confinement and surfaces decorated with methyl groups provides high recognition of CO2 molecules through multiple van der Waals interactions. The column breakthrough experiments suggest that Zn-ox-mtz dramatically achieved the one-step purification capacity of C2H2 from the CO2/C2H2 mixture with a record C2H2 productivity of 2091 mmol kg-1, surpassing all of the CO2-selective adsorbents reported so far. In addition, Zn-ox-mtz exhibits excellent chemical stability under different pH values of aqueous solutions (pH = 1-12). Moreover, the highly stable framework and excellent inverse selective CO2/C2H2 separation performance showcase its promising application as a C2H2 splitter for industrial manufacture. This work paves the way to developing reverse-selective adsorbents for the challenging gas separation process.

Leveraging Metal Nodes in Metal-Organic Frameworks for Advanced Anodic Hydrazine Oxidation Assisted Seawater Splitting.

Metal-organic frameworks (MOFs) show great promise for electrocatalysis owing to their tunable ligand structures. However, the poor stability of MOFs impedes their practical applications. Unlike the general pathway for engineering ligands, we report herein an innovative strategy for leveraging metal nodes to improve both the catalytic activity and the stability. Our electrolysis cell with a NiRh-MOF||NiRh-MOF configuration exhibited 10 mA cm-2 at an ultralow cell voltage of 0.06 V in alkaline seawater (with 0.3 M N2H4), outperforming its counterpart benchmark Pt/C||Pt/C cell (0.12 V). Impressively, the incorporation of Rh into a MOF secured a robust stability of over 60 h even when working in the seawater electrolyte. Experimental results and theoretical calculations revealed that Rh atoms serve as the active sites for hydrogen evolution while Ni nodes are responsible for the hydrazine oxidation during the hydrazine oxidation assisted seawater splitting. This work provides a paradigm for green hydrogen generation from seawater.

Application of metal-organic frameworks, covalent organic frameworks and their derivates for the metal-air batteries

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) as the novel porous materials have the merits of diverse, adjustable functionality, high porosity and surface area, which have great application prospects in the gas storage, separation and catalysis. In addition, their derivates make up for the insufficient of electronic conductivity and chemical stability of MOFs and COFs, and provide a new ideal for accurate control of material structure. Up to now, many efficient electrocatalysts have been designed based on MOFs, COFs and their derivates for O₂ reduction/evolution reactions (ORR/OER) and CO₂ reduction/evolution reactions (CO₂RR/CO₂ER) in the metal-air batteries. In this review, the latest development of MOFs, COFs and their derivates in the metal-air batteries is summarized, and we discuss the structural characteristics of these materials and their corresponding mechanisms of action. By comprehensively reviewing the advantages, challenges and prospects of MOFs and COFs, we hope that the organic framework materials will shed more profound insights into the development of electrocatalysis and energy storage in the future.

A microporous water stable MOF for consistent and selective C2H2/C2H4 separation

Polymer-grade ethylene production requires the removal of trace acetylene, which possesses an intractable industrial separation task. Metal-organic frameworks (MOFs) having stability in water/moisture-containing environments are the promising alternative physisorbent material for the purification of C2H4 from C2H2-containing mixtures. In this study, a three-dimensional MOF (IITKGP-30) with narrow pore channels (∼4.5 × 4.5 Å2) is developed for C2H2/C2H4 separation exhibiting excellent IAST separation selectivity of 3.3 (1:99) and 6.2 (50:50) at 295 K under 1 bar. Theoretical investigation revealed preferentially binding of acetylene molecules to the metal site in an end-on fashion equivalent to 4.76 kJ mol−1 more binding energy than ethylene. Dynamic breakthrough experiments with 1:99 (v/v) C2H2/C2H4 mixtures at 298 K revealed a complete separation of the binary mixture with excellent breakthrough selectivity of 2.4 and the ethylene productivity of 10.4 mL g−1. It is highly stable under 97% RH as long as 15 days and in the presence of water, can maintain a C2H2 uptake and retention time minimum up to three breakthrough cycles with ease of regenerability, thus showing its great promise for practical deployment.

Immobilization of Gold Nanoparticles on Postsynthetically Modified NU-1000 for Hydrogen Evolution Reaction

NU-1000, being a hydrothermally stable metal-organic framework (MOF), with structural robustness is viable for functionalization with various entities. A postsynthetic modification strategy called solvent-assisted ligand incorporation (SALI) is chosen for functionalizing NU-1000 with thiol moieties using 2-mercaptobenzoic acid. In accordance with soft acid-soft base interactions, the thiol groups on NU-1000, as a scaffold, can immobilize the gold nanoparticles without much aggregation. The catalytically active gold sites on thiolated NU-1000 are utilized for hydrogen evolution reaction (HER). The catalyst delivered an overpotential of 101 mV at a current density of 10 mAcm-2 in 0.5 M H2SO4. The faster charge transfer kinetics determined from the Tafel slope of 44 mV/dec enhances the HER activity. The sustainable performance of the catalyst for 36 h proves its utility as a potential catalyst to produce neat hydrogen.

Ortho Effects of Tricarboxylate Linkers in Regulating Topologies of Rare-Earth Metal-Organic Frameworks.

A linker design strategy is developed to attain novel polynuclear rare-earth (RE) metal-organic frameworks (MOFs) with unprecedented topologies. We uncover the critical role of ortho-functionalized tricarboxylate ligands in directing the construction of highly connected RE MOFs. The acidity and conformation of the tricarboxylate linkers were altered by substituting with diverse functional groups at the ortho position of the carboxyl groups. For instance, the acidity difference between carboxylate moieties resulted in forming three hexanuclear RE MOFs with novel (3,3,3,10,10)-c wxl, (3,12)-c gmx, and (3,3,3,12)-c joe topologies, respectively. In addition, when a bulky methyl group was introduced, the incompatibility between the net topology and ligand conformation guided the co-appearance of hexanuclear and tetranuclear clusters, generating a novel 3-periodic MOF with a (3,3,8,10)-c kyw net. Interestingly, a fluoro-functionalized linker prompted the formation of two unusual trinuclear clusters and produced a MOF with a fascinating (3,8,10)-c lfg topology, which could be gradually replaced by a more stable tetranuclear MOF with a new (3,12)-c lee topology with extended reaction time. This work enriches the polynuclear clusters library of RE MOFs and unveils new opportunities to construct MOFs with unprecedented structural complexity and vast application potential.

Endowing Porphyrinic Metal-Organic Frameworks with High Stability by a Linker Desymmetrization Strategy.

The fabricating of metal-organic frameworks (MOFs) that integrate high stability and functionality remains a long-term pursuit yet a great challenge. Herein, we develop a linker desymmetrization strategy to construct highly stable porphyrinic MOFs, namely, USTC-9 (USTC represents the University of Science and Technology of China), presenting the same topological structure as the well-known PCN-600 that readily loses crystallinity in air or upon conventional activation. For USTC-9, the involved porphyrinic linker (TmCPP-M) with carboxylate groups located in the meta-position presents a chair-shaped conformation with lower C2h symmetry than that (D4h) of the common porphyrinic carboxylate (TCPP) linker in PCN-600. As a result, the wrinkled and interlocked linker arrangements collectively contribute to the remarkable stability of USTC-9. Given the high stability and porosity as well as Lewis acidity, USTC-9(Fe) demonstrates its excellent performance toward catalytic CO2 cycloaddition with diverse epoxides at moderate temperature and atmospheric pressure.

Dynamic Bond-Directed Synthesis of Stable Mesoporous Metal–Organic Frameworks under Room Temperature

Stable metal-organic frameworks (MOFs) with mesopores (2-50 nm) are promising platforms for immobilizing nanosized functional compounds, such as metal-oxo clusters, metal-sulfide quantum dots, and coordination complexes. However, these species easily decompose under acidic conditions or high temperatures, hindering their in situ encapsulation in stable MOFs, which are usually synthesized under harsh conditions involving excess acid modulators and high temperatures. Herein, we report a route for the room-temperature and acid-modulator-free synthesis of stable mesoporous MOFs and MOF catalysts with acid-sensitive species encapsulated: (1) we initially construct a MOF template by connecting stable Zr6 clusters with labile Cu-bipyridyl moieties; (2) Cu-bipyridyl moieties are subsequently exchanged by organic linkers to afford a stable version of Zr-MOFs; (3) acid-sensitive species, including polyoxometalates (POMs), CdSeS/ZnS quantum dots, and Cu-coordination cages, can be encapsulated in situ into the MOFs during step 1. The room-temperature synthesis allows the isolation of mesoporous MOFs with 8-connected Zr6 clusters and reo topology as kinetic products, which are inaccessible by traditional solvothermal synthesis. Furthermore, acid-sensitive species remain stable, active, and locked within the frameworks during MOF synthesis. We observed high catalytic activity for VX degradation by the POM@Zr-MOF catalysts as a result of the synergy between redox-active POMs and Lewis-acidic Zr sites. The dynamic bond-directed method will accelerate the discovery of large-pore stable MOFs and offer a mild route to avoid the decomposition of catalysts during MOF synthesis.