Sandwich template derived porous ZnO@gCN heterostructure nanocomposites and the enhanced photocatalytic efficiency in oxidative coupling of amines

Abstract The construction of heterostructure composites is an efficient way to widen the spectral response range and reduce the photogenerated electrons-holes recombination, but it is still a challenge to realize the maximizing the photocatalytic performance of different photoresponsive material, especially at low temperature. In this work, we construct a series of ZnO@gCN-UA/MA composites by first designing a series of UA@ZIF-8@MA sandwich templates and then calcining these sandwich templates at high temperature. During the pyrolysis process, ZIF-8 and melamine precursors would convert into ZnO and gCN structure so as to form the ZnO@gCN composite at high temperature, while urea molecular would decompose to release ammonia molecules which rush out from the interior of ZIF-8 to make the ZnO@gCN-UA/MA composites become fluffy and porous. Detailed characterization results reveal that the ZnO@gCN-UA/MA composites exhibit enhanced spectral response range and the lower charge-carrier recombination rates. When being used in photocatalytic oxidative coupling of amines at low temperature under air condition, the optimal ZnO(0.1)@gCN-UA/MA catalyst exhibits excellent activity, affording the imine product with 96% yield. Moreover, the catalysts also exhibit a wide substrate compatibility and recyclability.