Multimetal-MOF-derived transition metal alloy NPs embedded in an N-doped carbon matrix: highly active catalysts for hydrogenation reactions

Abstract

Transition metal NPs and their alloy NPs have attracted significant attention due to their low cost and potential to replace noble-metal-based catalysts in many reaction systems; however, major challenges are still encountered when exploring cost-effective and scaleable strategies to prepare and attach them with optimal supports for maximizing their catalytic efficiency. Here, we report a facile and repeatable route to synthesize transition metal based nano-catalysts by first developing a series of new and novel N-donor multimetallic M–M′-MOFs [(M–M′(1,4-bdc)₂(dabco)]·4DMF·1/2H₂O, M/M′ = Co, Ni, Cu) by a facile mixed-metal approach and then directly pyrolyzing these hetero-nuclear MOFs under inert gas. In the pyrolysis process, the transition metal ions (two of Co, Ni, and Co) of M–M′-MOFs could be transformed into transition alloy nanoparticles while the surrounding N-containing ligands were polymerized to N-doped graphitic carbon, resulting in highly dispersed M/M′ alloy NPs embedded in the N-doped carbon matrix. The detailed characterization results revealed that the metal elements including Co, Ni, and Cu were uniformly distributed in every individual alloy NP and there existed an obvious synergetic activation of different transition metals and strong coordination interactions between metals of alloy NPs and N atoms. When being used in the transfer hydrogenation of nitriles in the absence of basic additives, the optimal Co–Ni(3 : 1)@C–N showed the best catalytic performance with 100% conversion of benzonitrile and over 98% yield for the desired product, which was almost 5 times more active than its monometallic counterparts. We believe that this MOF-templating strategy provides a facile and controllable route for the preparation of nanocatalysts based on transition metal NPs with high transfer hydrogenation performance.