A novel conductive 3D covalent organic framework for high-performance trimethylamine gas sensing at room temperature

With the rapid expansion of the Internet of Things (IoT) and portable electronic technologies, the demand for gas sensors combining high performance, low operating temperatures, and strong environmental tolerance has become increasingly pressing in both environmental monitoring and medical diagnostics. Trimethylamine (TMA), a volatile amine released from spoiled seafood and markedly elevated in the exhaled breath of chronic kidney disease patients, serves as an essential biomarker of food spoilage and metabolism-related disorders. Herein, a three-dimensional (3D) conductive covalent organic framework (TFS-MnPor-COF) with a 2-fold interpenetrated network topology was synthesized via Schiff-base condensation using metal porphyrin units, exhibiting a large surface area, exposed Mn-N₄ sites, hierarchical pores, and excellent conductivity. For the first time, integrating TFS-MnPor-COF into flexible devices enabled a high-performance TMA sensor operating at room temperature with low power consumption, fast response/recovery (72/81 s), wide detection range (0.02-700 ppm), and low detection limit (7.1 ppb). X-ray photoelectron spectroscopy and in-situ Fourier transform infrared analysis revealed that oxygen chemisorption modulated the surface depletion layer, leading to changes in resistance upon TMA exposure. Overall, this work introduces a novel 3D COF-based strategy for high-performance gas sensing and provides a promising approach for volatile organic compound detection.