Isomorphous Substitution of Organic Cage Crystal by Pd Nanoclusters for Selective Hydrogenation

Abstract

For supporting active metal, the cavity confinement and mass transfer facilitation lie not in one sack, a trade‐off between high activity and good stability of the catalyst is present. Porous organic cages (POCs) are expected to break the trade‐off when metal particles are properly loaded. Herein, three organic cages (CC3, RCC3, and FT‐RCC3) are employed to support Pd nanoclusters for catalytic hydrogenation. Subnanometer Pd clusters locate differently in different cage frameworks by using the same reverse double‐solvents approach. Compared with those encapsulated in the intrinsic cavity of RCC3 and anchored on the outer surface of CC3, the Pd nanoclusters orderly assembled in FT‐RCC3 crystal via isomorphous substitution exhibit superior activity, high selectivity, and good stability for semi‐hydrogenation of phenylacetylene. Isomorphous substitution of FT‐RCC3 crystal by Pd nanoclusters is originated from high crystallization capacity of FT‐RCC3 and specific interaction of each Pd nanocluster with four cage windows. Both confinement function and H2 accumulation capacity of FT‐RCC3 are fully utilized to support active Pd nanoclusters for efficient selective hydrogenation. The present results provide a new perspective to the heterogeneous catalysis field in terms of crystalizing metal nanoclusters in POC framework and outside the cage for making the best use of both parts.