Efficient Syngas Photoproduction Enabled by Electronic Engineering of Co‐Immobilized Imine COFs

Abstract

ABSTRACT Heterogeneous photocatalytic CO 2 reduction provides a promising route for syngas production. However, high reaction energy barriers and inefficient charge separation and transfer hinder the surface CO 2 reduction. Herein, on a covalent organic framework (COF) based catalyst, through the enhanced photoelectron transfer efficiency by introduction of N atoms, also the increased electron density of the Co (II) site with two negative one‐valent bidentate ligands, we achieved both ultrahigh syngas production rate and high H 2 /CO molar ratio. The best catalyst in this work: Triazine‐COF‐Co‐SA enabled a record‐high syngas production rate with high H 2 /CO molar ratio (≥2) of 698.7 mmol g −1 h −1 . Femtosecond transient absorption spectroscopy (fs‐TAS), in situ infrared spectroscopy (In situ IR) and theoretical calculation indicated that N introduction to the framework and active site electron density increasing were effective for the previous challenges. On Triazine‐COF‐Co‐SA, the energy barrier was lowered from 1.90 to 0.54 eV, also fs‐TAS showed an obvious τ 4 = 1.5 ns which represented a higher charge transfer efficiency. This study shows great potential for catalyst modification on COF‐based catalysts to enhance CO 2 photoreduction capability.