Controllably solar-driven C‒C coupling organic synthesis integrated with H2 production over P-doped g-C3N4 with NiS nanoparticles modification

Abstract

The development of mild and environmental method for direct transformation of aromatic alcohol into hydrobenzoin via controlled C‒C coupling is a highly attractive but challenging goal. In this paper, a P-doped g-C3N4 photocatalyst with NiS nanoparticles modification is first reported to apply the visible-light-driven C‒C coupling of aromatic alcohol into hydrobenzoin, as well as integrating with the production of clean H2 fuel. The synergistic effect of doped P atoms and formed type-II heterojunction between PCN and NiS improves the light absorption ability of g-C3N4 and greatly suppresses the charge recombination. Optimized 2.0% NiS/PCN composite achieves the complete conversion of aromatic alcohol within 6 h reaction time, as far as we known, which is the highest efficiency so far for aromatic alcohol conversion via photocatalytic strategy. Hydrobenzoin is controllably formed with 68% selectivity, together with a highly-efficient H2 production rate of 994.8 μmol·g−1·h−1. In-situ EPR studies reveal a preferential activation of C‒H bond than O‒H bond in aromatic alcohol by photoexcited holes, forming C6H5ĊH2OH radicals for subsequent coupling. The residual protons interact with photoexcited electrons to generate H2. Our study not only offers an efficient g-C3N4-based photocatalyst for the synthesis of hydrobenzoin under mild conditions, but also opens up a new avenue for manipulating the activation of C‒H or O‒H bonds for high selectivity of hydrobenzoin product.