Constructing Nitrogen Self-Doped Covalent Triazine-Based Frameworks for Visible-Light-Driven Photocatalytic Conversion of CO2 into CH4

Photocatalytic reduction of carbon dioxide to hydrocarbon fuel provides a sustainable strategy for addressing the increasing energy crisis as well as alleviating the greenhouse effect. Yet, seeking effective, affordable, and metal-free photocatalysts is still a challenging issue. Herein, a novel nitrogen self-doped covalent triazine-based framework (NCTF-1) was prepared via a simple hydrothermal process for photocatalytic CO2 reduction to CH4 using visible light. NCTF-1 exhibited a CH4 evolution rate of 11.48 μmol g–1 h–1, corresponding to ninefold enhancement, compared with bare covalent triazine-based frameworks (CTF-1). The photocatalytic enhancement mechanism was probed by a variety of instrumental measurements. Results showed that the modification of nitrogen atoms in NCTF-1 could extend the responsive range of the visible-light spectrum, promote CO2 capture, and thus greatly elevate the photocatalytic CO2 reduction activity. Notably, NCTF-1 displayed a satisfactory selectivity for CO2 conversion with CH4 accounting for over 85% of the reduction products. This study offers a promising avenue for achieving robust CO2-to-CH4 conversion and provides insight into the impact of nitrogen self-doping on covalent triazine-based frameworks.