Utilization of the solar light for clean energy conversion has been well accepted as one of the promising technologies and strategies to overcome the energy crisis. Amongst a variety of materials developed as photocatalysts, metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) have attracted high attention due to the highly porous structure and the adjustability in both structure and functionality. These materials have been applied in particular for photocatalytic CO₂ reduction to address the greenhouse effect and energy shortage, photocatalytic water splitting and H₂ evolution, and photocatalytic organic redox transformations for certain chemicals demand in industry. In this review, recent advances in the field of MOF- and COF-based materials for photocatalytic CO₂ reduction, H₂ evolution and organic redox transformations are discussed. More importantly, significant attention is given to the proposed mechanisms for MOF and COF-based materials as photocatalysts. The strategies for boosting photocatalytic performance are identified and systematically summarized. In the end, a brief outlook towards specific unresolved problems and several perspectives on the characterization and mechanism study are proposed. We hope that this review can afford a comprehensive understanding of the applications of MOFs and COFs in photocatalysis and stimulate scientists to address remaining challenges to develop this field further.