A Modulator‐Induced Defect‐Formation Strategy to Hierarchically Porous Metal–Organic Frameworks with High Stability

The pore size enlargement and structural stability have been recognized as two crucial targets, which are rarely achieved together, in the development of metal–organic frameworks (MOFs). Herein, we have developed a versatile modulator‐induced defect‐formation strategy, in the presence of monocarboxylic acid as a modulator and an insufficient amount of organic ligand, successfully realizing the controllable synthesis of hierarchically porous MOFs (HP‐MOFs) with high stability and tailorable pore characters. Remarkably, the integration of high stability and large mesoporous property enables these HP‐MOFs to be important porous platforms for applications involving large molecules, especially in catalysis.     

Template‐Directed Approach Towards the Realization of Ordered Heterogeneity in Bimetallic Metal–Organic Frameworks

Controlling the arrangement of different metal ions to achieve ordered heterogeneity in metal–organic frameworks (MOFs) has been a great challenge. Herein, we introduce a template‐directed approach, in which a 1D metal–organic polymer incorporating well‐defined binding pockets for the secondary metal ions used as a structural template and starting material for the preparation of well‐ordered bimetallic MOF‐74s under heterogeneous‐phase hydrothermal reaction conditions in the presence of secondary metal ions such as Ni²⁺ and Mg²⁺ in 3 h. The resulting bimetallic MOF‐74s were found to possess a nearly 1:1 metal ratio regardless of their initial stoichiometry in the reaction mixture, thus demonstrating the possibility of controlling the arrangement of metal ions within the secondary building blocks in MOFs to tune their intrinsic properties such as gas affinity.     

Selective Catalytic Chemistry at Rhodium(II) Nodes in Bimetallic Metal–Organic Frameworks

We report the first study of a gas‐phase reaction catalyzed by highly dispersed sites at the metal nodes of a crystalline metal–organic framework (MOF). Specifically, CuRhBTC (BTC^3?=benzenetricarboxylate) exhibited hydrogenation activity, while other isostructural monometallic and bimetallic MOFs did not. Our multi‐technique characterization identifies the oxidation state of Rh in CuRhBTC as +2, which is a Rh oxidation state that has not previously been observed for crystalline MOF metal nodes. These Rh²⁺ sites are active for the catalytic hydrogenation of propylene to propane at room temperature, and the MOF structure stabilizes the Rh²⁺ oxidation state under reaction conditions. Density functional theory calculations suggest a mechanism in which hydrogen dissociation and propylene adsorption occur at the Rh²⁺ sites. The ability to tailor the geometry and ensemble size of the metal nodes in MOFs allows for unprecedented control of the active sites and could lead to significant advances in rational catalyst design.     

A Noble‐Metal‐Free Metal–Organic Framework (MOF) Catalyst for the Highly Efficient Conversion of CO2 with Propargylic Alcohols

Cyclization of propargylic alcohols with CO₂ is an important reaction in industry, and noble‐metal catalysts are often employed to ensure the high product yields under environmentally friendly conditions. Herein a porous noble‐metal‐free framework 1 with large 1D channels of 1.66 nm diameter was synthesized for this reaction. Compound 1 exhibits excellent acid/base stability, and is even stable in corrosive triethylamine for one month. Catalytic studies indicate that 1 is an effective catalyst for the cyclization of propargylic alcohols and CO₂ without any solvents under mild conditions, and the turnover number (TON) can reach to a record value of 14 400. Furthermore, this MOF catalyst also has rarely seen catalytic activity when the biological macromolecule ethisterone was used as a substrate. Mechanistic studies reveal that the synergistic catalytic effect between Cu^I and In^III plays a key role in the conversion of CO₂.     

Long‐Term Photostability in Terephthalate Metal–Organic Frameworks

Prolonged (weeks) UV/Vis irradiation under Ar of UiO‐66(Zr), UiO66 Zr‐NO₂, MIL101 Fe, MIL125 Ti‐NH₂, MIL101 Cr and MIL101 Cr(Pt) shows that these MOFs undergo photodecarboxylation of benzenedicarboxylate (BDC) linker in a significant percentage depending on the structure and composition of the material. Routine characterization techniques such as XRD, UV/Vis spectroscopy and TGA fail to detect changes in the material, although porosity and surface area change upon irradiation of powders. In contrast to BCD‐containing MOFs, zeolitic imidazolate ZIF‐8 does not evolve CO₂ or any other gas upon irradiation.