Porous Composite‐Mediated Bimetallic Cluster POMs/Zr‐MOF for Catalytic Transfer Hydrogenation of Biomass‐Derived Aldehydes and Ketones

Abstract

AbstractSynergistic catalytic effects and metal node modulation are pivotal to the performance of multifunctional catalysts.We present a versatile strategy for constructing bimetallic M1M2 cluster catalysts (polyoxometalates (POMs)/Zr‐based metal‐organic frameworks (Zr‐MOF); M1 = Zr; M2 = W, V, Mo) by a microwave‐assisted in‐situ precoordination‐postmodification approach, which consisted of the grafting of POM single clusters onto Zr–O clusters of hierarchical porous composites (defective Zr‐MOF (HUiO‐66x)) and the modulation of metal nodes in Zr‐MOF. Hierarchical porosity and double active centers in the POMs/Zr‐MOF result in greater accessibility to catalytic sites and adjustable acid–base properties, thus providing opportunities for the catalytic transfer hydrogenation of biomass‐derived aldehydes/ketones. The synergistic acid–base couple sites (W6+–O2−–Zr4+) not only bridge hydrogen donors into the reaction system but also promote the dissociation of α‐C(sp3)‐H from isopropanol and subsequent hydrogen transfer to the activated carbonyl in furfural. Enhanced substrate adsorption and decreased activation barrier of the rate‐determining step are keys for the direct hydrogen transfer from carbonyl compounds to near‐quantitative corresponding alcohols via an eight‐membered‐ring transition state to achieving unprecedented low‐temperature catalytic performance over bimetallic Zr–W clusters. The proposed general method of bimetallic cluster catalysts reveals the roles of accessible metal modulation and synergistic catalytic centers toward specific catalysis.