Monolayer-Assisted Surface-Initiated Schiff-Base-Mediated Aldol Polycondensation for the Synthesis of Crystalline sp<sup>2</sup> Carbon-Conjugated Covalent Organic Framework Thin Films
Ke Wang, Haoyong Yang, Zhongquan Liao, Shengxu Li, Mike Hambsch, Guangen Fu, Stefan C. B. Mannsfeld, Qi Sun, Tao Zhang
Abstract
sp 2 carbon-conjugated covalent organic frameworks (sp 2 c-COFs) with superb in-plane π-conjugations, high chemical stability, and robust framework structure are expected to be ideal films/membranes for a wide range of applications including energy-related devices and optoelectronics. However, so far, sp 2 c-COFs have been mainly limited to microcrystalline powders, and this consequently hampered their performances in devices. Herein, we report a simple and robust methodology to fabricate large-area, free-standing, and crystalline sp 2 c-COF films (TFPT–TMT and TB–TMT) on various solid substrates (e.g., fluorine-doped tin oxide, aluminum sheet, polyacrylonitrile membrane) by self-assembly monolayer-assisted surface-initiated Schiff-base-mediated aldol polycondensation (namely, SI-SBMAP). The resultant sp 2 c-COF films show lateral sizes up to 120 cm 2 and tunable thickness from tens of nanometers to a few micrometers. Owing to the robust framework and highly ordered quasi-1D channels, the sp 2 c-COF membrane-based osmotic power generator presents an output power density of 14.1 W m –2 under harsh conditions, outperforming most reported COF membranes as well as commercialized benchmark devices (5 W m –2 ). This work demonstrates a simple and robust interfacial methodology for the fabrication of sp 2 c-COF films/membranes for green energy applications and potential optoelectronics.