Direct Z-Scheme Heterojunction Catalysts Constructed by Graphitic-C(3)N(4) and Photosensitive Metal-Organic Cages for Efficient Photocatalytic Hydrogen Evolution

The demand for improving the activity, durability, and recyclability of metal-organic cages (MOCs) that work as photocatalytic molecular devices in a homogeneous system has promoted research to combine them with other solid materials. An M(2)L(4) type photosensitive metal-organic cage MOC-Q2 with light-harvesting ligands and catalytic Pd(2+) centers has been synthesized and further heterogenized with graphitic carbon nitride to prepare a robust direct Z-scheme heterojunction photocatalyst for visible-light-driven hydrogen generation. The optimized g-C(3)N(4)/MOC-Q2 (0.7 wt%) sample exhibits a high H(2) evolution activity of 6423 μmol g(−1) h(−1) in 5 h, and a total turnover number of 39,695 after 10 h, significantly superior to the bare MOC-Q2 used in the homogeneous solution and the comparison sample Pd/g-C(3)N(4)/L-4. The enhanced performances of g-C(3)N(4)/MOC-Q2 can be ascribed to its direct Z-scheme heterostructure, which effectively improves the charge separation and transfer efficiency. This work presents a rational approach of designing a binary photocatalytic system through combing micromolecular MOCs with heterogeneous semiconductors for water splitting.