Embedding Nitrogen Heteroatoms into Nanoporous Benzothiadiazole-Based Covalent Organic Frameworks for Boosting Photocatalytic Oxidative Coupling of Amines

Abstract

Two-dimensional covalent organic frameworks (2D COFs) have attracted increasing research attention in photocatalysis-related fields due to their high porosity, large surface area, and tunable band gap. The construction of effective and robust 2D COFs for improving photocatalytic activity of 2D COFs is highly desirable. Herein, we propose a strategy for promoting photocatalytic oxidative activity of 2D COFs via doping nitrogen into donor units. Two novel benzothiadiazole-based 2D COFs with kgm topology, namely COF−BD and COF−BP, have been successfully synthesized by reacting tetratopic 5,5'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diisophthalaldehyde with ditopic benzidine and [2,2'-bipyridine]-5,5'-diamine, respectively. Interestingly, the as-synthesized COF−BP exhibited better performances in photocatalytic oxidative coupling of amines than the corresponding COF−BD. Moreover, the resultant COF−BP exhibited excellent recyclability after being used for ten cycles. Mechanistic investigations revealed that the introduction of electron-withdrawing nitrogen atoms into donor units is favorable for enhancing visible-light absorption, narrowing the band gap, and facilitating the separation and transport of the photogenerated carriers of 2D COFs. This work provides an effective approach for the design of 2D COFs for advanced photocatalytic organic transformations.

Keywords

Covalent organic frameworks / Nitrogen heteroatoms / Donor-acceptor / Benzothiadiazole / Photocatalysis

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2025 SIOC, CAS, Shanghai, & WILEY-VCH GmbH