Microenvironment regulation via nitrogen atoms in covalent organic frameworks for enhanced selective photocatalysis

Abstract

Covalent organic frameworks (COFs), with desirable properties and high designability, exhibit promising application prospects in photocatalysis. Rational molecular engineering is critical for boosting photocatalytic activity, wherein meticulous regulation of the COF microenvironment becomes imperative. Herein, the condensation of 2,4,6-triformylphloroglucinol (Tp) with 1,3,5-tris(4-aminophenyl)triazine (TAPT), 5,5′,5′′-(benzene-1,3,5-triyl)tris(pyridin-2-amine) (BTPy), and 5,5′,5′′-(benzene-1,3,5-triyl)tris(pyrimidin-2-amine) (BTPm) affords three highly crystalline and porous COFs, TpTAPT-COF, TpBTPy-COF, and TpBTPm-COF, respectively. Nitrogen atom microenvironment regulation endows TpBTPm-COF with exceptional optoelectronic properties, enabling efficient photogenerated carrier separation and transfer. Consequently, the photocatalytic activity for the selective generation of sulfoxides from sulfides under blue LED irradiation follows the order TpBTPm-COF > TpBTPy-COF > TpTAPT-COF. Essentially, both electron and energy transfers govern the selective oxidation of sulfides over TpBTPm-COF. Overall, this work establishes atomic-level microenvironment regulation in COFs as a general principle for designing crystalline photocatalysts.