Enhancing Photocatalytic Transfer Semi-Hydrogenation of Alkynes Over Pd/C 3 N 4 Through Dual Regulation of Nitrogen Defects And Mott-Schottky Effect.

The selective hydrogenation of alkynes is an important reaction; however, the catalytic activity and selectivity in this reaction are generally conflicting. In this study, ultrafine Pd nanoparticles (NPs) loaded on a graphite-like C 3 N 4 structure with nitrogen defects (Pd/DCN) were synthesized. The resulting Pd/DCN exhibited excellent photocatalytic performance in the transfer hydrogenation of alkynes with ammonia borane. The reaction rate and selectivity of Pd/DCN were superior to those of Pd/BCN (bulk C 3 N 4 without nitrogen defects) under visible light irradiation. The characterization results and density functional theory calculations showed that the Mott-Schottky effect in Pd/DCN could change the electronic density of the Pd NPs, and thus enhanced the hydrogenation selectivity toward phenylacetylene. After 1 h, the hydrogenation selectivity of Pd/DCN reached 95%, surpassing that of Pd/BCN (83%). Meanwhile, nitrogen defects in the supports improved the visible-light response and accelerated the transfer and separation of photogenerated charges to enhance the catalytic activity of Pd/DCN. Therefore, Pd/DCN exhibited higher efficiency under visible light, with a turnover frequency (TOF) of 2002 min -1 . This TOF was five times that of Pd/DCN under dark conditions and 1.5 times that of Pd/BCN. This study provides new insights into the rational design of high-performance photocatalytic transfer hydrogenation catalysts. This article is protected by copyright. All rights reserved.