Polymer Brush-Mediated Surface-Initiated Polycondensation Enables sp2C-COF Thin Films with Controlled Crystallinity and High Photocatalytic Performance

Sp2-carbon-conjugated covalent organic frameworks (sp2C-COFs) hold exceptional potential as π-conjugated semiconductors for optoelectronics and photocatalysis, yet their thin-film fabrication suffers from irreversible C = C linkages that impede crystallinity and morphology control. Herein, we report a polymer brush-mediated surface-initiated polycondensation (PB-SIP) strategy to synthesize the sp2C-COF films with controlled crystallinity and morphology. The polymer brush layer acts as both a surface-tethered initiator and a soft interfacial regulator, enabling precise control over nucleation and crystallization kinetics. By modulating the polymer brush thickness, we achieve sp2C-COF films with enhanced crystallinity and reduced surface roughness. Notably, this method allows the growth of highly crystalline, homogeneous sp2C-COF coatings on 3D porous sponges, which exhibit near-complete photocatalytic antibacterial efficiency (99.4%) in natural sewage under visible light. This interfacial engineering paradigm advances the rational design of crystalline sp2C-COF films for energy-environment applications. Conjugated covalent organic frameworks (COF) hold exceptional potential as semiconductors for optoelectronics and photocatalysis, but control over crystallinity and morphology remains challenging. Here the authors report a polymer brush- mediated surface-initiated polycondensation strategy to synthesize the conjugated COF films with controlled crystallinity and morphology.