Desymmetric Design Directs the Synthesis of Covalent Organic Framework Isomers with Divergent Topology and Photocatalytic Performance

The topology of covalent organic frameworks (COFs) is a pivotal factor in governing their photocatalytic performance. However, the targeted synthesis of topological isomers is often hindered by the high symmetry of conventional building units and the stringent reaction conditions. Herein, we employed a desymmetrized A 2 B 2 -type imidazole-based monomer (BDI), featuring divergent angles of approximately 75° and 105°, to construct COF isomers with distinct topologies. The asymmetric geometry of the BDI monomer facilitates diverse spatial connectivity, enabling the formation of not only a conventional rhombic sql lattice with AA stacking (BDI-COF-S) but also a specific topology extended from a sql net with an uncommon AB stacking mode (BDI-COF-NT). The specific structure of BDI-COF-NT promoted efficient charge transfer and reduced the exciton binding energy, resulting in a H 2 O 2 photosynthesis rate approximately double that of BDI-COF-S in both pure water and a water/benzyl alcohol (9:1) system. BDI-COF-NT achieved a high H 2 O 2 generation yield of 51.56 mmol g –1 h –1 in the biphasic system, surpassing those of most reported COF-based catalysts. Meanwhile, the generated H 2 O 2 enabled efficient and stable degradation of organic pollutants such as rhodamine B (RhB) and methylene blue (MB), indicating practical sewage treatment potential. This work underscores the potential of molecular-level topology engineering to diversify the structural landscape of COFs and optimize their photocatalytic functionality.