Liquid Crystal Induced Large‐Area Continuous Covalent Organic Framework Films for High‐Performance Humidity Sensors

ABSTRACT Large‐area, continuous covalent organic framework (COF) films are in high demand for the fabrication of high‐performance humidity sensors. However, conventional synthetic approaches of COF films are still plagued by drawbacks, such as harsh reaction conditions, film fragility, and time‐consuming processes. Herein, we report a novel liquid crystal (LC)‐assisted fabrication of large‐area COF films, which exhibits remarkable universality for the synthesis of distinct types of COF films. Mechanistic investigations reveal that non‐covalent interactions induced by LC molecules facilitate the dense packing and ordered self‐assembly of organic precursors, thereby overcoming the bottleneck of large‐scale film fragmentation. Featuring a response time of 4.45 s (15%–90% RH), recovery time of 1.95 s (90%–15% RH), and sensitivity of 13.90 m Ω/%RH, the COF film‐based humidity sensor exhibits fast response and excellent durability. Overall, this work provides a versatile strategy to synthesize large‐area COF films, enabling the construction of high‐performance humidity sensors and thereby offering guidance for the development of high‐performance active layers for humidity sensors.