Ultra‐Strong Janus Covalent Organic Framework Membrane with Smart Response to Organic Vapor

Vapor‐driven smart Janus materials have made significant advancements in intelligent monitoring, control, and interaction, etc. Nevertheless, the development of ultrafast response single‐layer Janus membrane, along with a deep exploration of the smart response mechanisms, remains a long‐term endeavor. Here, the successful synthesis of a high‐crystallinity single‐layer Covalent organic framework (COF) Janus membrane is reported by morphology control. This kind of membrane displays superior mechanical properties and specific surface area, along with excellent responsiveness to CH2Cl2 vapor. The analysis of the underlying mechanisms reveals that the vapor‐induced breathing effect of the COF and the stress mismatch of the Janus structure play a crucial role in its smart deformation performance. It is believed that this COF Janus membrane holds promise for complex tasks in various fields. The single‐layer COF Janus membrane, morphologically tuned, exhibits mechanical strength on par with Kevlar. This membrane demonstrates rapid and reversible actuation upon exposure to CH2Cl2 vapor, heralding potential in smart material applications. Notably, this study reveals the first observation of vapor‐induced actuation in COF membranes.