Constructing Heterogeneous Direct Z-Scheme Photocatalysts Based on Metal-Organic Cages and Graphitic-C3N4 for High-Efficiency Photocatalytic Water Splitting

The development of artificial devices that mimic the highly efficient and ingenious photosystems in nature is worthy of in-depth study. A metal-organic cage (MOC) Pd-2(M-4)(4)(BF4)(4), denoted as MOC-Q1, integrating four organic photosensitized ligands M-4 and two Pd2+ catalytic centers is designed for a photochemical molecular device (PMD). MOC-Q1 is successfully immobilized on graphitic carbon nitride (g-C3N4) by hydrogen bonds to obtain a robust heterogeneous direct Z-scheme g-C3N4/MOC-Q1 photocatalyst for H-2 generation under visible light. The optimized g-C3N4/MOC-Q1 (2 wt %) system shows high hydrogen evolution activity (4495 mu mol g(-1)h(-1) based on the catalyst mass) and exhibits stable performances for 25 h (a turnover number of 19,268 based on MOC-Q1), significantly outperforming pure MOC-Q1, g-C3N4, and comparsion materials Pd/g-C3N4/M-4, which is the highest one of all reported heterogeneous MOC-based photocatalysts under visible irradiation. This enhancement can be ascribed to the synergistic effects of high-efficient electron transfer, extended visible-light response region, and good protective environment for MOC-Q1 arising from an efficient direct Z-scheme heterostructure of g-C3N4/MOC-Q1. This rationally designed and synthesized MOC/g-C3N4-based heterogeneous PMD is expected to have great potential in photocatalytic water splitting.

Automated summary

The study focuses on developing artificial devices that mimic the highly efficient and ingenious photosystems in nature. A metal-organic cage (MOC) Pd-2(M-4)(4)(BF4)(4) designed for a photochemical molecular device (PMD) shows significantly enhanced hydrogen evolution activity under visible light, outperforming other comparison materials. This rationally designed and synthesized MOC/g-C3N4-based heterogeneous PMD is expected to have great potential in photocatalytic water splitting.