Rational Synthesis of Extended π‐Conjugated Covalent Organic Frameworks for Enhanced Photocatalytic Uranium(VI) Removal

Atom‐level control of π‐conjugations in covalent organic frameworks (COFs) facilitates deep exploration of the relationship between electron‐transport properties and photocatalysis, which is particularly important for improving photocatalytic performance. Herein, we present a comprehensive strategy for the synthesis of extended π‐conjugated COFs via a one‐pot tandem Scholl cyclization‐dehydrogenation reaction. The extended π‐conjugated COFs are constructed by planar covalent bonds, in which imine linkers are converted to imine‐cyclized counterparts, resulting in all chemical bonds conjugatively connected throughout the framework. Subsequently, benzene units are substituted with naphthalene units to yield an even more highly extended π‐conjugated framework. These approaches ensure that delocalized electrons efficiently transport across the COF framework with extended π‐conjugation, resulting in extended‐range light absorption, improved electron‐hole separation, and more efficient charge‐carrier utilization under visible‐light irradiation. Notably, the extended π‐conjugated COFs exhibit remarkable photocatalytic performance in uranium(VI) removal from contaminated water sources, surpassing the performance of electron‐deficient p‐π‐conjugated counterparts. These findings demonstrate a new general design strategy for the synthesis of highly‐conjugated COF photocatalysts. The strategy is expected to provide new insights into the rational design of high‐performance COFs for applications in photocatalysis, including water‐source decontamination and potentially numerous other applications.