Large Triazine Organic Cage Encapsulating Pd Nanoclusters for Selective Hydrogenation of Alkynes
Minghui Zhang, Ruichen Liu, Zexing He, Li Wang, Xiangwen Zhang, Guozhu Li
Abstract
Selective hydrogenation of alkynes is still hard due to the trade-off between high activity and infusive selectivity while maintaining good stability. Organic cages with a tunable cavity size and specific functional groups are competitive candidates for support for effectively regulating the size and electronic state of Pd clusters. Herein, various organic cages with different sizes ([4 + 6 and 8 + 12]) and functional groups (triazine, imine, and tertiary amine) are synthesized, on which Pd nanoclusters are loaded for catalyzing selective hydrogenation of alkynes. The [8 + 12] organic cage possessing 1,3,5-triazine groups successfully encapsulates a Pd nanocluster in its cavity. On the large-sized triazine organic cage-encapsulated Pd nanocluster, a unique coordination environment is present, the electronic state of Pd is modified, and the adsorption of phenylacetylene is improved. The as-prepared catalyst (Pd@TMC1) exhibits superior activity for the selective hydrogenation of phenylacetylene with a conversion of 95% and a styrene selectivity of 95% after 10 cycles. Pd@TMC1 also showed good universality for selective hydrogenation of acetylene compounds with different substituting groups. The present study provides a fresh reference for modifying the molecular architecture of organic cages on demand and utilizing them in heterogeneous catalysis.