Donor–Acceptor Type Carbon Nitride Photocatalysts in Photocatalysis: Current Understanding, Applications and Challenges

The exploration of photocatalytic materials with efficient charge separation has always been a prominent area of research in photocatalysis. In the preceding years, the strategy of constructing donor-acceptor (D-A) structured materials has gradually been developed in photocatalytic systems, becoming a new research crossroads and attracting extensive interdisciplinary focus. Polymeric carbon nitride (PCN) has gradually been recognized as the primary photocatalytic material for constructing D-A structures due to its attractive exceptional physicochemical stability, electronic band structure, and cost-effectiveness. However, few reports have summarized the research on D-A type PCN at the molecular level. This review focuses on the molecular level design strategies and the performance enhancement mechanisms of D-A type PCN are emphasized from two main aspects: intramolecular D-A and intermolecular D-A. In addition, the concept of dual D-A type PCN is introduced, proposing a new direction for advancing the efficacy of photocatalysts. Subsequently, this review summarizes the application scenarios of D-A type PCN in energy transformation and environmental amelioration. Finally, by elaborating on the main difficulties and opportunities in this hot field, this review can provide inspiration and innovative strategies for developing D-A type PCN and resolving energy and environmental issues.