2D-2D TiO2/anthracene-based covalent organic framework for visible-light-harnessed photocatalytic H2 generation and CO2 reduction.

Heterojunction photocatalysts are well recognized for their high efficiency in photocatalytic applications. In this study, we report the successful development of a β-ketoenamine-linked anthracene-based COF as a visible-light absorbing unit, which was integrated with TiO2 nanoparticles via an in situ growth approach to construct a TiO2@AntCOF hybrid photocatalytic system. The resulting 2D-2D TiO2@AntCOF heterostructure exhibited significantly higher photocatalytic activity compared to pristine TiO2 and the AntCOF, achieving an optimal H2 evolution rate of 730 μmol g-1 under visible light irradiation, which is 12 times higher than that of the pure AntCOF. In addition, the system demonstrated CO2 reduction rates of 1199 and 989 μmol g-1 for formic acid and formaldehyde, respectively. The formation of covalent bonds between TiO2 and the AntCOF was found to facilitate efficient charge transfer, as evidenced by TRPL, EIS, and LSV analyses. Mott-Schottky and EPR studies further supported a plausible type-II heterojunction charge transfer mechanism, accounting for the superior photocatalytic performance. The heterojunction photocatalyst was comprehensively characterized using FT-IR, PXRD, BET, XPS, SEM, and TEM, and its photocatalytic performance was systematically evaluated. Moreover, the TiO2@AntCOF exhibited excellent stability over six consecutive cycles, proving its potential as an efficient and cost-effective hybrid photocatalyst for sustainable H2 production and CO2 reduction.