Recent advances in metal-free covalent organic frameworks for photocatalytic applications in energy and environmental fields

Abstract

Covalent organic frameworks (COFs) are an emerging class of multivacancy organic polymers with a large specific surface area, stable pore size, high crystallinity, and good stability. Moreover, the tailorability of the structure provides a theoretical basis for the preparation of various COF-based materials. However, many COFs rely on metal ions to enhance their photocatalytic performance. Therefore, considering environmental factors and the necessity for developing COF applications, an in-depth review on metal-free COF photocatalysts from an environmental perspective is urgently needed. This review provides a comprehensive overview of the synthesis strategy of COFs, and the applications of metal-free COFs as photocatalysts in environmental fields, including water splitting, CO2 reduction, pollutant degradation, organic synthesis and environmental remediation. Otherwise, the review summarizes the current and future development of the field and provides perspectives on trends for future challenges and outlooks.