Truxenone-based donor-acceptor covalent organic framework incorporated with metal sites for enhanced photocatalytic CO2 reduction

Abstract

Photocatalytic reduction of carbon dioxide (CO2) into valuable chemicals offers a potential strategy to alleviate the environmental pollution, which has attracted great attention. Covalent organic frameworks (COFs) are known as a novel class of more promising materials to boost CO2 reudction is still an enormous chanllenging. Incorporating metal sites into COFs serves as a strategic design for product selectivity regulation since it increases the number of active sites. Herein, the electron donor-acceptor (D-A) structured truxenone (TRO)-based COFs with biphenyl (BPD-COF) and bipyridine units (BPY-COF) are constructed through a simple Schiff-base reaction, which offer a coordination environment for the metal ions and facilitate the adsorption and activation of CO2 molecules. Therefore, the photocatalytic CO production rate for the optimal sample of BPY-COF-Co is up to 870 μmol g-1 among 3 h, and the selectivity under visible light is 100%, over 9-fold higher than that of the pristine BPY-COF. Experimental and theoretical results reveal that under the synergistic effect of D-A structure and metal active sites facilitates the charge transfer and separation abilities to enhance photocatalytic CO2 reduction. This study offers molecular-level perspectives into mechanistic understanding in enhancing photocatalytic CO2 reduction reaction (CO2RR).