Donor-Acceptor Polyimide Covalent Organic Frameworks for Photocatalytic Generation of Singlet Oxygen and Superoxide Anion Radicals

Singlet oxygen and superoxide anion radicals represent two key active species in photocatalytic reactions. However, most conventional catalysts depend exclusively on one of these species or necessitate altered reaction conditions to access different active intermediates. In this work, we designed and synthesized three novel two-dimensional polyimide-based covalent organic frameworks (COFs), in which the electron-donating phthalocyanine and electron-accepting benzothiadiazole units are closely stacked, forming an alternating π-column architecture. These donor-acceptor COFs exhibit pronounced spatial charge separation, which not only promotes charge-carrier separation and electron transport but also narrows the energy gap between singlet and triplet excited states, enhances intersystem crossing (ISC) efficiency, and enables the simultaneous and efficient execution of both electron-transfer and energy-transfer processes. Consequently, this study not only expands the potential for functionalizing highly stable 2D COFs but also offers new perspectives on the conversion of solar energy into chemical energy using COF-based systems.