Pore‐Environment Engineering with Multiple Metal Sites in Rare‐Earth Porphyrinic Metal–Organic Frameworks

Multi‐component metal–organic frameworks (MOFs) with precisely controlled pore environments are highly desired owing to their potential applications in gas adsorption, separation, cooperative catalysis, and biomimetics. A series of multi‐component MOFs, namely PCN‐900(RE), were constructed from a combination of tetratopic porphyrinic linkers, linear linkers, and rare‐earth hexanuclear clusters (RE₆) under the guidance of thermodynamics. These MOFs exhibit high surface areas (up to 2523 cm² g^?1) and unlimited tunability by modification of metal nodes and/or linker components. Post‐synthetic exchange of linear linkers and metalation of two organic linkers were realized, allowing the incorporation of a wide range of functional moieties. Two different metal sites were sequentially placed on the linear linker and the tetratopic porphyrinic linker, respectively, giving rise to an ideal platform for heterogeneous catalysis.     

Electrochemical Exfoliation of Pillared‐Layer Metal–Organic Framework to Boost the Oxygen Evolution Reaction

Two‐dimensional (2D) materials and ultrathin nanosheets are advantageous for elevating the catalysis performance and elucidating the catalysis mechanism of heterogeneous catalysts, but they are mostly restricted to inorganic or organic materials based on covalent bonds. We report an electrochemical/chemical exfoliation strategy for synthesizing metal–organic 2D materials based on coordination bonds. A catechol functionalized ligand is used as the redox active pillar to construct a pillared‐layer framework. When the 3D pillared‐layer MOF serves as an electrocatalyst for water oxidation (pH 13), the pillar ligands can be oxidized in situ and removed. The remaining ultrathin (2 nm) nanosheets of the metal–organic layers are an efficient catalyst with overpotentials as low as 211 mV at 10 mA cm^?2 and a turnover frequency as high as 30 s^?1 at an overpotential of 300 mV.     

Oxidation reactions catalysed by molybdenum(VI) complexes grafted on UiO‐66 metal–organic framework as an elegant nanoreactor

A heterogeneous catalyst was synthesized by immobilizing Mo(CO)₃ in a UiO‐66 metal–organic framework. The benzene ring of the organic linker in UiO‐66 was modified via liquid‐phase deposition of molybdenum hexacarbonyl, Mo(CO)₆, as starting precursor to form the (arene)Mo(CO)₃ species inside the framework. The structure of this catalyst was characterized using X‐ray diffraction, and chemical integrity was confirmed using Fourier transform infrared and diffuse reflectance UV–visible spectroscopic methods. The metal content was analysed with inductively coupled plasma. Field emission scanning electron microscopy was used to measure particle size and N₂ adsorption measurements to characterize the specific surface area. This catalytic system was efficiently applied for epoxidation of alkenes and oxidation of sulfides. The Mo‐containing metal–organic framework was reused several times without any appreciable loss of its efficiency.     

A Mononuclear CoII Coordination Complex Locked in a Confined Space and Acting as an Electrochemical Water‐Oxidation Catalyst: A “Ship‐in‐a‐Bottle” Approach

Preparing efficient and robust water oxidation catalyst (WOC) with inexpensive materials remains a crucial challenge in artificial photosynthesis and for renewable energy. Existing heterogeneous WOCs are mostly metal oxides/hydroxides immobilized on solid supports. Herein we report a newly synthesized and structurally characterized metal–organic hybrid compound [{Co₃(μ₃‐OH)(BTB)₂(dpe)₂} {Co(H₂O)₄(DMF)₂}_0.5]_n?n H₂O ( Co‐WOC‐1 ) as an effective and stable water‐oxidation electrocatalyst in an alkaline medium. In the crystal structure of Co‐WOC‐1 , a mononuclear Co^II complex {Co(H₂O)₄(DMF)₂}²⁺ is encapsulated in the void space of a 3D framework structure and this translationally rigid complex cation is responsible for a remarkable electrocatalytic WO activity, with a catalytic turnover frequency (TOF) of 0.05 s^?1 at an overpotential of 390 mV (vs. NHE) in 0.1 m KOH along with prolonged stability. This host–guest system can be described as a “ship‐in‐a‐bottle”, and is a new class of heterogeneous WOC.     

Boosting the Catalytic Performance of Metal–Organic Frameworks for Steroid Transformations by Confinement within a Mesoporous Scaffold

Solid‐state crystallization achieves selective confinement of metal–organic framework (MOF) nanocrystals within mesoporous materials, thereby rendering active sites more accessible compared to the bulk‐MOF and enhancing the chemical and mechanical stability of MOF nanocrystals. (Zr)UiO‐66(NH₂)/SiO₂ hybrid materials were tested as efficient and reusable heterogeneous catalysts for the synthesis of steroid derivatives, outperforming the bulk (Zr)UiO‐66(NH₂) MOF. A clear correlation between the catalytic activity of the dispersed Zr sites present in the confined MOF, and the loading of the mesoporous SiO₂, is demonstrated for steroid transformations.     

Selective Capture of Toxic Selenite Anions by Bismuth‐based Metal–Organic Frameworks

Chemically durable and effective absorbent materials for selenite (SeO₃^2?) remain highly desirable for contamination remediation. Now a bismuth‐based metal–organic framework (Bi‐MOF, CAU‐17) was used as adsorbent to capture SeO₃^2? anions from aqueous solution with ultrahigh adsorption capacity of 255.3 mg g^?1 and fast kinetics. Furthermore, the adsorbent showed excellent selectivity for SeO₃^2? and was able to work steadily in a broad pH range of 4–11. Density functional theory (DFT) calculation, XANES modeling, and EXAFS fitting suggested that SeO₃^2? anions were immobilized by forming Bi?O?Se bonds (T‐3 structural model) though splitting the O?Bi?O bond in the crystal structure, leading to a structural transformation of CAU‐17 in the solid state.     

A stable pillared metal–organic framework constructed by H4TCPP ligand as luminescent sensor for selective detection of TNP and Fe3+ ions

A novel luminescent metal–organic framework ( Zn‐TCPP/BPY ) with pillared structure based on 2,3,5,6‐tetrakis(4‐carboxyphenyl)pyrazine (H₄TCPP) and 4,4′‐bipyridine (BPY) has been designed and synthesized through a solvothermal reaction. The [Zn₂(COO)₄] paddlewheel units are linked by TCPP^4? ligands to form two‐dimensional layers and further connected by BPY ligands as pillars to construct the twofold interpenetrating three‐dimensional framework. Interestingly, Zn‐TCPP/BPY possesses outstanding stability in organic solvents and water as well as maintains its structural rigidity in aqueous solutions of different pH values (3–12). After activation, Zn‐TCPP/BPY possesses permanent porosity with Brunauer–Emmett–Teller surface area of 630 m² g^–1. Remarkably, Zn‐TCPP/BPY displays excellent fluorescent property in virtue of the aggregation‐induced emission effect of the H₄TCPP ligand, which can be highly active and quenched by small amounts of 2,4,6‐trinitrophenol (TNP) and Fe³⁺ ions. Furthermore, the detection effect of Zn‐TCPP/BPY remains basically the same even after five cycles. The excellent stability, high sensitivity, and recyclability of Zn‐TCPP/BPY make it an outstanding chemical sensor for detecting TNP and Fe³⁺ ions.     

A new luminescent anionic metal–organic framework based on heterometallic zinc(II)–barium(II) for selective detection of Fe3+ and Cu2+ ions in aqueous solution

Over the past two decades, the development of novel inorganic–organic hybrid porous crystalline materials or metal–organic frameworks (MOFs) using crystal engineering has provoked significant interest due to their potential applications as functional materials. In this context, luminescent MOFs as fluorescence sensors have recently received significant attention for the sensing of ionic species and small molecules. In this work, a new luminescent heterometallic zinc(II)–barium(II)‐based anionic metal–organic framework, namely poly[imidazolium [triaqua(μ₆‐benzene‐1,3,5‐tricarboxylato)bariumtrizinc] tetrahydrate], {(C₃H₄N₂)[BaZn₃(C₉H₃O₆)₃(H₂O)₃]·4H₂O}_n ( 1 ), was synthesized under hydrothermal conditions and characterized. Compound 1 presents a three‐dimensional framework with an unprecedented (3,5)‐connected topology of the point symbol (3.9²).(3³.4².5.9³.10), and exhibits `turn‐off' luminescence responses for the Cu²⁺ and Fe³⁺ ions in aqueous solution based on significantly different quenching mechanisms.     

Structural Transformation in Metal–Organic Frameworks for Reversible Binding of Oxygen

Polycyclic aromatic derivatives can trap ¹O₂ to form endoperoxides (EPOs) for O₂ storage and as sources of reactive oxygen species. However, these materials suffer from structural amorphism, which limit both practical applications and fundamental studies on their structural optimization for O₂ capture and release. Metal–organic frameworks (MOFs) offer advantages in O₂ binding, such as clear structure–performance relationships and precise controllability. Herein, we report the reversible binding of O₂ is realized via the chemical transformation between anthracene‐based and the corresponding EPO‐based MOF. It is shown that anthracene‐based MOF, the framework featuring linkers with polycyclic aromatic structure, can rapidly trap ¹O₂ to form EPOs and can be restored upon UV irradiation or heating to release O₂. Furthermore, we confirm that photosensitizer‐incorporated anthracene‐based MOF are promising candidates for reversible O₂ carriers controlled by switching Vis/UV irradiation.     

Mild and Selective Catalytic Hydrogenation of the C=C Bond in α,β‐Unsaturated Carbonyl Compounds Using Supported Palladium Nanoparticles

Chemoselective reduction of the C=C bond in a variety of α,β‐unsaturated carbonyl compounds using supported palladium nanoparticles is reported. Three different heterogeneous catalysts were compared using 1 atm of H₂: 1) nano‐Pd on a metal–organic framework (MOF: Pd⁰‐MIL‐101‐NH₂(Cr)), 2) nano‐Pd on a siliceous mesocellular foam (MCF: Pd⁰‐AmP‐MCF), and 3) commercially available palladium on carbon (Pd/C). Initial studies showed that the Pd@MOF and Pd@MCF nanocatalysts were superior in activity and selectivity compared to commercial Pd/C. Both Pd⁰‐MIL‐101‐NH₂(Cr) and Pd⁰‐AmP‐MCF were capable of delivering the desired products in very short reaction times (10–90 min) with low loadings of Pd (0.5–1 mol %). Additionally, the two catalytic systems exhibited high recyclability and very low levels of metal leaching.     

Semiconducting Clathrates Meet Gas Hydrates: Xe24[Sn136]

Semiconducting Group 14 clathrates are inorganic host–guest materials with a close structural relationship to gas hydrates. Here we utilize this inherent structural relationship to derive a new class of porous semiconductor materials: noble gas filled Group 14 clathrates (Ng_x[M₁₃₆], Ng=Ar, Kr, Xe and M=Si, Ge, Sn). We have carried out high‐level quantum chemical studies using periodic Local‐MP2 (LMP2) and dispersion‐corrected density functional methods (DFT‐B3LYP‐D3) to properly describe the dispersive host–guest interactions. The adsorption of noble gas atoms within clathrate‐II framework turned out to be energetically clearly favorable for several host–guest systems. For the energetically most favorable noble gas filled clathrate, Xe₂₄[Sn₁₃₆], the adsorption energy is ?52 kJ mol^?1 per guest atom at the LMP2/TZVPP level of theory, corresponding to ?9.2 kJ mol^?1 per framework Sn atom. Considering that a hypothetical guest‐free Sn clathrate‐II host framework is only 2.6 kJ mol^?1 per Sn atom less stable than diamond‐like α‐Sn, the stabilization resulting from the noble gas adsorption is very significant.     

Gem‐dinitromethyl‐substituted Energetic Metal–Organic Framework based on 1,2,3‐Triazole from in situ Controllable Synthesis

Synthesizing energetic metal–organic frameworks at ambient temperature and pressure has been always a challenge in the research area of energetic materials. In this work, through in situ controllable synthesis, energetic metal–organic framework gem‐dinitromethyl‐substituted dipotassium 4,5‐bis(dinitromethyl)‐1,2,3‐triazole with a “cage‐like” crystal packing was obtained and characterized. Most importantly, for the first time, we found that it could be successfully afforded with a catalytic effect of trifluoroacetic acid. This new compound exhibited its high density (2.04 g cm^?3) at ambient temperature, superior detonation velocity (8715 m s^?1) to that of lead azide (5877 m s^?1) and comparable to that of RDX (8748 m s^?1). Its detonation products are mainly N₂ (48.1 %), suggesting it is also a green energetic material. The above‐mentioned performance indicates its potential applications in detonator devices as lead‐free primary explosive.     

Porous GdIII‐Organic Framework as a Dual‐Functional Material for Cyanosilylation of Aldehydes and Ablation of Human Liver Cancer Cells

Metal‐organic frameworks (MOFs) have gained great attention in recent years because they could behave as multifunctional materials which combine the advances of porous solids and coordination complexes. With the aim of constructing multifunctional MOFs, in this study, we choose a Y‐shaped tricarboxylic ligand biphenyl‐3,4′,5‐tricarboxylic acid (H₃bpt) to react with Gd^III ions to afford a new dual‐functional lanthanide‐organic framework with the chemical formula of [Gd₂(bpt)₂(H₂O)₂] · (DMF)₂(H₂O)₆ ( 1 ) (DMF = N,N‐dimethylformamide) under solvothermal condition. The title complex was characterized by means of elemental analysis, FT‐IR spectroscopy, thermogravimetric and X‐ray diffraction analyses. Crystal structure analysis reveals that compound 1 is composed of 1D helical chain secondary building units that connect by the bpt^3– ligands into a 3D framework with 1D nanosized channels running along the b axis. In view of its high porosity and accessible open metal sites, the activated 1 ( 1a ) was studied for the cyanosilylation of aldehydes under solvent‐free conditions. The catalytic activity of 1a is much higher than that of compound 1 , indicating that the exposed open metal sites of 1a is beneficial to the cyanosilylation reaction. In connection to these, the different cytotoxicities of 1 and 1a were also evaluated on four human liver cancer cells (SMMC‐7721, Bel‐7402, MHCC97 and Hep3B) by the MTT assay.     

A Metal–Organic Framework with Exceptional Activity for C−H Bond Amination

The development of catalysts capable of fast, robust C?H bond amination under mild conditions is an unrealized goal despite substantial progress in the field of C?H activation in recent years. A Mn‐based metal–organic framework (CPF‐5) is described that promotes the direct amination of C?H bonds with exceptional activity. CPF‐5 is capable of functionalizing C?H bonds in an intermolecular fashion with unrivaled catalytic stability producing >10⁵ turnovers.     

Turning Redundant Ligands into Treasure: A New Strategy for Constructing MIL‐53(Al)@Nanoscale TiO2 Layers

A strategy for in situ fabrication of nanoscale‐thin layers of anatase TiO₂ coated on the metal–organic framework (MOF) material, MIL‐53(Al), is developed. The preparation conditions for crystallized TiO₂ are normally incompatible with the thermal and chemical stability of MOFs. Based on our strategy, we found that the redundant organic ligands (1,4‐benzenedicarboxylic acid, H₂BDC) within the pores of the as‐synthesized MOF play a key function in the protection and support of the framework during hydrothermal loading of the TiO₂ precursor, as well as in preventing the infiltration of the precursor into the pores. After annealing, a nanoscale‐thin layer of highly crystalline anatase TiO₂, with a thickness of 6–10 nm, was successfully attached to the external surface of the MIL‐53(Al) crystals, while the porous framework remains intact. The core–shell structure of the MOF@TiO₂ nanocomposite endows the resulting materials with additional optical response and enhanced moisture and chemical stability.     

Microporous La–Metal–Organic Framework (MOF) with Large Surface Area

A microporous La–metal‐organic framework (MOF) has been synthesized by the reaction of La(NO₃)₃ ? 6 H₂O with a ligand 4,4′,4′′‐s‐triazine‐1,3,5‐triyltri‐p‐aminobenzoate (TATAB) featuring three carboxylate groups. Crystal structure analysis confirms the formation of 3D MOF with hexagonal micropores, a Brunauer–Emmett—Teller (BET) surface area of 1074 m² g^?1 and high thermal and chemical stability. The CO₂ adsorption capacities are 76.8 cm³ g^?1 at 273 K and 34.6 cm³ g^?1 at 293 K, a highest measured CO₂ uptake for a Ln–MOFs.     

Polyoxometalate‐Based Entangled Coordination Networks Induced by an Extended Bis(triazole) Ligand

The introduction of an extended bridging bis(triazole) ligand, that is, 4,4′‐bis(1,2,4‐triazol‐1‐ ylmethyl)biphenyl (BBPTZ), into the hydrothermal reaction system containing transition metal ions and Keggin‐type polyoxometalates (POMs) led to the isolation of three new organic–inorganic hybrid entangled coordination networks, [Cu^I₂Cu^II(BBPTZ)₆][SiW₁₂O₄₀]?12 H₂O ( 1 ), [Ni(BBPTZ)₂(H₂O)][H₂SiW₁₂O₄₀]?11 H₂O ( 2 ), and [Ni₂(BBPTZ)₄(H₂O)₂][SiW₁₂O₄₀]?3 H₂O ( 3 ). All three compounds were characterized by elemental analysis, IR spectroscopy, TG analysis, powder X‐ray diffraction, and single‐crystal X‐ray diffraction. Compound 1 contains a 2‐D POM‐based metal–organic layer entangled with 1‐D ladder‐like metal–organic chains. The adjacent 2‐D networks are parallel to each other, further stacking into a 3‐D supramolecular framework with 1‐D channels. Compound 2 exhibits a 1‐D cantilever‐type loop‐containing chain. The Keggin‐type POMs act as the cantilever groups, leading to the adjacent catilever‐type chains interwaving together to form a 3‐D supramolecular open framework with two types of channels. Compound 3 possesses a 3‐D open framework based on 2‐D metal–organic undulated layer and Keggin‐type POM clusters. Three sets of such frameworks further interpenetrate with each other to form an interesting three‐fold interpenetrating framework. The photocatalytic activities of compounds 1–3 for the decomposition of methylene blue (MB) under UV light have been investigated.     

Synthesis,Structure, and Photoluminescent Properties of a New 3D Metal‐Organic Framework with Unusual AgI Chains

A new 3D metal‐organic framework {[Ag₄(btc)(bix)₂] · H₂O}_n ( 1 ) [H₄btc = biphenyl‐2, 2′,4, 4′‐tetracarboxylic acid, bix = 1, 4‐bis(imidazol‐1‐ylmethyl)benzene] was synthesized under hydrothermal conditions and characterized by single‐crystal X‐ray diffraction, infrared (IR) spectroscopy, thermal gravimetric analysis (TGA), and luminescence studies. The most remarkable structural feature of 1 is that the 1D chain and 2D network interpenetrated structures are further linked by parallel aligned 1D Ag^I chains to generate 3D metal‐organic framework.     

A Highly Energetic N‐Rich Metal–Organic Framework as a New High‐Energy‐Density Material

Metal–organic framework (MOF)‐based energetic material [Cu₃(MA)₂(N₃)₃] ( 1 ; MA=melamine) was synthesized and structurally characterized (47.55 % N). The structural analysis revealed the existence of unusual multiwalled tubular channels and interweaving of single and double helical units in 1 . The standard molar enthalpy of formation was found to be 1788.73 kJ mol^?1, which is the highest value among previously reported MOF‐based energetic materials. The calculated detonation properties showed that 1 can be used as a potential explosive. Sensitivity tests revealed that 1 is insensitive and thus can function as a high‐energy‐density material with a favorable level of safety.     

Metal–Organic Gel Material Based on UiO‐66‐NH2 Nanoparticles for Improved Adsorption and Conversion of Carbon Dioxide

Metal–organic frameworks (MOFs) including the UiO‐66 series show potential application in the adsorption and conversion of CO₂. Herein, we report the first tetravalent metal‐based metal–organic gels constructed from Zr^IV and 2‐aminoterephthalic acid (H₂BDC‐NH₂). The ZrBDC‐NH₂ gel materials are based on UiO‐66‐NH₂ nanoparticles and were easily prepared under mild conditions (80 °C for 4.5 h). The ZrBDC‐NH₂‐1:1‐0.2 gel material has a high surface area (up to 1040 m² g^?1) and showed outstanding performance in CO₂ adsorption (by using the dried material) and conversion (by using the wet gel) arising from the combined advantages of the gel and the UiO‐66‐NH₂ MOF. The ZrBDC‐NH₂‐1:1‐0.2 dried material showed 38 % higher capture capacity for CO₂ at 298 K than microcrystalline UiO‐66‐NH₂. It showed high ideal adsorbed solution theory selectivity (71.6 at 298 K) for a CO₂/N₂ gas mixture (molar ratio 15:85). Furthermore, the ZrBDC‐NH₂‐1:1‐0.2 gel showed activity as a heterogeneous catalyst in the chemical fixation of CO₂ and an excellent catalytic performance was achieved for the cycloaddition of atmospheric pressure of CO₂ to epoxides at 373 K. In addition, the gel catalyst could be reused over multiple cycles with no considerable loss of catalytic activity.