Isomeric Covalent Organic Frameworks for High‐Efficiency Photocatalytic CO <sub>2</sub> Reduction: Substituent Position Effect
Wenliang Song, Su-Di Chen, Xitong Ren, Xi Su, Chongping Song, Yusen Li, Long Chen, Feng Bai
Abstract
Abstract The exploration of covalent organic frameworks (COFs) for high‐efficiency photocatalytic CO 2 reduction is urgently demanded. Herein, COF‐based catalysts are constructed for the selective photoreduction of CO 2 to CO via delicately designed isomeric monomers with substituent at the 4,5,9,10‐ positions (K) or 1,3,6,8‐positions (A) of pyrene knots. The distinct substituted regions significantly affect the planarity of pyrene knots, resulting in COFs with different microstructures and photocatalytic activities. While employing a 5 W LED white‐light as the light source, the single atomic Co contained A‐Py‐Bpy‐COF‐Co showcased a moderate CO evolution rate of 2174.4 µmol g −1 h −1 . In sharp contrast, K‐Py‐Bpy‐COF‐Co reveals a considerable CO photo‐reduction rate of 12 476.4 µmol g −1 h −1 (5.7 times higher than A‐Py‐Bpy‐COF) with a selectivity up to 93.3%. Remarkably, the excellent photocatalytic activity of K‐Py‐Bpy‐COF‐Co can be maintained for at least 5 cycles without obvious decay. The distinct photocatalytic properties of the two isomeric COFs can be attributed to the larger steric‐hindrance of K‐Py‐4CHO which enlarges the interlayer distances to inhibit exciton quenching and electron‐richer nature of monatomic Co in K‐Py‐Bpy‐COF‐Co. This work provides a new protocol to explore COFs with boosted photocatalytic performance via isomeric design from refined modulation of reported COFs.