Bandgap engineering of covalent triazine frameworks for highly efficient and selective photoreduction of CO2 to CO

Abstract

Covalent triazine frameworks (CTFs) have emerged as promising photocatalytic platforms for CO₂ conversion, favored for their tunable bandgap and ease of processing. In this study, a series of CTFs were synthesized by altering polymer chain lengths through the incorporation of phenyl units at the metal positions of the triazine rings. This structural modification facilitated precise control over the band positions and bandgap energies of the CTFs. Experimental evaluations and theoretical predictions confirmed that these modifications efficiently catalyze CO₂ reduction to CO under full-spectrum irradiation, using water vapor as an electron donor under ambient conditions without the need for sacrificial agents, organic solvents, co-catalyst or photosensitizers. Among the variants, the optimized CTF 2 demonstrated a CO evolution rate of 103.4 μmol g⁻¹ within 4 h which is 7.3 and 2.8 times greater than comparable CTFs, while achieving an exceptional CO selectivity of 99.95 %. This research lays the groundwork for efficient CO₂ photoreduction using organic semiconductor catalysts and highlighting the critical role of precise bandgap control through structural tuning.