Expanded Synthesis of 3D Covalent Organic Frameworks via Linker Exchange for Efficient Photocatalytic Aerobic Oxidation

Abstract Despite recent progress in 3D covalent organic frameworks (3D‐COFs), their design and synthesis still pose significant challenges, mainly due to a limited mechanistic understanding of their synthesis. Herein, a linker exchange approach has been utilized to synthesize a series of new 3D‐COFs by first preparing an imine‐linked 3D‐COF followed by exchanging with selected linear diamine linkers. This approach can be widely applicable to different types of diamines, enabling rational‐designed synthesis of 3D frameworks that are previously inaccessible via direct polymerization in a one‐pot reaction. Mechanistic aspects associated with the improved 3D‐COF synthesis via the linker exchange approach, are investigated by density functional theory calculations, in which the possibility of the departure of the leaving linker is a spontaneous process with a decrease in enthalpy. Catalytic and computational results revealed that incorporating benzoxazole moiety into the 3D‐COF frameworks enables a significant increase in the capability of visible‐light‐driven catalysis. The overall findings of the present study will pave the way toward the development of 3D‐COFs with tunable structures and functions for other promising and challenging applications.