Thioether functionalized vinylene-linked covalent organic frameworks boost the semi-hydrogenation selectivity of alkynes

Covalent organic frameworks (COFs) have been rapidly developed in heterogeneous catalysis due to their regular pore structure, customizable pore size, easy modification, and functionalization, as well as large specific surface area. In this work, we designed and synthesized thioether functionalized vinylene (-CHCH-)-linked COFs (V-COFs) with high crystallinity. Owing to the strong interaction of thioether and metals, Pd nanoparticles were successfully encapsulated in their ordered pores to produce Pd@V-COF-S, which was used as a catalyst for the selective semi-hydrogenation of a series of alkynes under mild conditions (30 degrees C, H-2 balloon), with phenylacetylene conversion (>99%) and styrene selectivity (>97%). Both experimental and theoretical calculation results substantiated that the thioether groups could enhance the metal-support interaction of the Pd nanoparticles and reduce the energy barrier of styrene desorption, which in turn improved the selectivity of the catalyst.