Visible-light-driven photocatalytic CO2 reduction over ketoenamine-based covalent organic frameworks: role of the host functional groups

Abstract

The photocatalytic conversion of CO₂ into valuable chemicals is a promising and sustainable approach for solving the worldwide environmental and energy problems. In the current work, a series of ketoenamine-based covalent organic frameworks (COFs) with different functional groups in the same host framework, named TpBD-X [X = –H₂, –(CH₃)₂, –(OCH₃)₂, and –(NO₂)₂], were synthesized to study how different functional groups affect the overall photocatalytic CO₂ reduction for the first time. The differences in morphology, light-absorption intensity, and band gap among these functionalized COFs were also investigated. Compared to the electron-withdrawing groups, the electron-donating groups in TpBD can have a stronger conjugation effect and accelerate photogenerated charge separation and transfer, thereby improving the photocatalytic performance for CO₂ reduction. This work is beneficial for the understanding of the effects of the functional groups on the light-absorption intensity, band gap, and charge transfer that are key parameters in photocatalysis, and therefore provides a new approach for designing efficient COF-based photocatalysts for CO₂ reduction.