Metal organic framework derived heteroatoms and cyano (CN) group co-decorated porous g-CN nanosheets for improved photocatalytic H evolution and uranium(VI) reduction.

The introduction of heteroatoms and functional groups in g-CN generally has great advantages in enhancing the photocatalytic performance. In this work, the heteroatoms (Zn + C) and cyano (CN) group co-decorated porous g-CN nanosheets (DCNNS) photocatalysts were successfully synthesized through direct calcination of the mixed urea and metal-organic frameworks. The optimized DCNNS displayed a maximum H evolution rate of ~484.09 μmol/h with a quantum efficiency of ~3.43% at 420 nm, and the photocatalytic U(VI) reduction activity was improved by ~6.09 times. The enhanced photocatalytic performance could be ascribed to following benefits: (1) the modified DCNNS shared the two-dimensional layered structure of g-CN, and the massive nanopores in the nanosheets provided more reaction sites and diffusion channels for accelerated mass transfer; (2) the formation of cyano group greatly broadened the light response range and also acted as strong electron-withdrawing group for improving the carrier separation rate; (3) heteroatoms doping modulated the band gap, increased the electric conductivity, promoted the carrier separation and transport, and prolonged the electron lifetime to enhance photocatalytic performance. This work suggested that the heteroatoms and functional groups co-decoration could significantly improve the performance of g-CN-based photocatalysts and hold great potential to be further explored for energy and environmental applications.