Gas-Template Synthesis of Ultrathin Porous Carbon Nitrides for Photocatalytic Redox Reactions

Graphitic carbon nitride (g-C₃N₄) has emerged as a promising metal-free photocatalyst but is plagued by its low activity owing to a high electron-hole recombination rate and small specific surface area. A specialized gas-template method was successfully employed to synthesize an ultrathin porous carbon nitride (UPCN) photocatalyst containing nitrogen vacancies. This thermally induced exfoliation and polycondensation approach can be modulated using different gas templates. Compared with bulk g-C₃N₄, UPCNs feature an optimized ultrathin structure, larger surface area, weaker fluorescence intensity, lower impedance, and higher photocurrent response. These properties contribute to more exposed active sites, shorter diffusion paths for both ions and electrons, and improved carrier separation. Consequently, UPCNs exhibit considerably enhanced photocatalytic performance in both the hydrogen evolution reaction (HER) and the photooxidation of 2,6-dimethyl-1,4-dihydro-3,5-pyridinedicarboxylic ester (1,4-DHP) under visible light. Among UPCNs, TPA-UPCN (tetrapropylammonium chloride as the gas template) exhibits the highest photocatalytic activity, surpassing NH₄Cl-templated carbon nitrides (2747 vs 2092 μmol·g^-1·h^-1) in HER. Moreover, TPA-UPCN achieves unprecedented photocatalytic oxidation efficiency for 1,4-DHP. This study provides a new approach for the preparation of UPCN materials with enhanced photocatalytic performance.