Sandwich-Structured Hybrid of NiCo Nanoparticles-Embedded Carbon Nanotubes Grafted on CN Nanosheets for Efficient Photodehydrogenative Coupling Reactions.

Exploring cheap and efficient hybrid catalysts offers exciting opportunities for enhancing the performance of photocatalysts in the green organic synthesis field. Herein, a facile and effective approach is designed for the synthesis of a sandwich-structured hybrid in which NiCo bimetallic nanoparticles are embedded in the tip of nitrogen-doped carbon nanotubes (N-CNTs) grafted on both sides of a nitrogen deficient CN (N-CN) nanosheet for photodehydrogenative coupling reactions. Such a brand-new type of sandwich-structured hybrid comprises N-CN nanosheets and surrounding N-CNTs embedded with NiCo nanoparticles at their tips. Remarkably, the resultant hybrid exhibits integrated functionalities, abundant active sites, enhanced visible light absorption, and excellent interfacial charge transfer ability. As a result, the optimized NiCo@N-CNTs@N-CN photocatalyst shows significantly improved photodehydrogenative coupling performance of amines to imines compared to the control single-metal-based catalysts (Ni@N-CNTs@N-CN and Co@N-CNTs@N-CN). The mechanistic investigation through experimental and computational study demonstrates that, compared with single-metal-based hybrids, the NiCo bimetallic hybrid exhibits stronger amine adsorption and weaker photogenerated hydrogen atom adsorption, thus promoting the dehydrogenative activation of primary amines and fast generation of imines. This work presents a promising insight for designing and preparing efficient photocatalysts to trigger organic synthesis in high yields.