Soft-Templated Synthesis of Large-Extrinsic-Mesopore Covalent Organic Frameworks with Tunable Pore Architecture and Size

Covalent organic frameworks (COFs) with large mesopores beyond their intrinsic micropores are highly desirable for advancing applications in catalysis, biocatalysis, and energy storage, etc. However, the bottom-up construction of such materials by soft template still remains challenging due to poor solvent compatibility, the easy expulsion of templates during crystallization and so on. Herein, by introducing suitable structure-directing agent and cosolvent to anchor and stabilize soft template micelle, respectively, as well as preactivating monomer to enhance the kinetics of the Schiff-base condensation, we successfully created well-defined large extrinsic mesopores for COFs with tunable pore architecture and size upon mild solution-based polymerization-induced self-assembly. This synergistic strategy ensured the micelle formation, stabilization and stronger interaction with monomers, and more importantly, effectively avoided being expulsed when confronted with crystallization stress. Also, by varying the cosolvent and incorporating a hydrophobic swelling agent, the mesopore architecture (spherical pores to ridged pores) and size (10.8 to 34.3 nm) can be precisely tuned. Such unique porous architecture provided COF with high iodine loading capacity and abundant active sites, as a cathode host in iodine batteries, which thus delivering excellent rate performance (e.g., retaining a capacity of 197 mAh g –1 at 0.5 A g –1 ) and long-term cycling stability (82.7% capacity retention after 1500 cycles).