Active Site Engineering in Reticular Covalent Organic Frameworks for Photocatalytic CO2 Reduction

Abstract Photochemical CO 2 reduction using ubiquitous sunlight akin to natural photosynthesis is an effective approach for conversion of renewable energy into useful chemical feedstock. Driven by the need for earth‐abundant, inexpensive, and sustainable photocatalysts with practical applicability, covalent organic frameworks (COFs) have emerged as a new generation of molecularly defined semiconductors with tunable optoelectronic properties. These reticular frameworks with highly ordered, porous and crystalline structures can be tailor‐made by covalently combining organic building blocks to target specific functions. To date, numerous COFs have been reported, which show promising activity for photocatalytic CO 2 reduction allowing to derive structure–property–function relationships. In this review, the different reported strategies are comprehensively analyzed and categorized for active site engineering in COF photocatalysts and the synthetic rationale and resulting catalytic activity for each approach are discussed. The recent advancements in terms of tailored photocatalyst design are then critically assessed, aspects of advanced materials characterization are analyzed, and future perspectives and challenges for the field are highlighted.