Gas Sensors with Two-Dimensional rGO@COF Composite Materials for Fast NO₂ Detection under Room Temperature

Covalent organic frameworks (COFs) are attracting increasing interest in various applications due to their ability to capture molecules originating from their highly crystallized porous structures. However, most types of COFs are non-conductive and cannot be directly applied to electronic devices. Herein, we utilize non-conductive COFs in chemiresistor sensors by forming composite structures with conductive reduced graphene oxide (rGO). The composites rGO@COF exhibit low-enough resistance to be measured as chemiresistors, demonstrating enhanced gas sensing performance than pristine rGO. In particular, rGO@COF sensors achieve 2.7 times higher sensitivity toward NO₂ and a dramatically reduced response time from 234 to 32 s compared to rGO, which can be attributed to increased surface area and NO₂ adsorption energy. Our strategy provides new perspectives for utilizing non-conductive COFs in various electronic applications.