Tailoring NH₃ Sensing Responsiveness through Amine Modification of Imine-Based Nanoporous Covalent Organic Polymer

An efficient and affordable NH 3 sensor is crucial for accurately monitoring atmospheric pollution and human health. Nanoporous covalent organic polymers (nCOPs) are promising candidates for detecting NH 3 due to their abundant functional groups on the surface, excellent electrical properties, and nanoporous structure. This enables precise detection with exceptional selectivity and sensitivity. Herein, we have developed an imine-containing nanoporous COP (nCOPI) and further reduced the imine bonds (C═N) to synthesize an amine (C–N)-containing nanoporous COP (nCOPA). We have employed these as sensing materials for detecting NH 3 at 25 °C. Interestingly, the nCOPA sensor displays an impressive 18.6 times increased response of 1700% toward 500 ppm of NH 3 compared to the nCOPI sensor (91%) with a response/recovery time of 60/70 s. Furthermore, the nCOPA sensor demonstrates exceptional selectivity, complete reversibility, excellent repeatability, and long-term stability, achieving limit of detection (LOD) and limit of quantification (LOQ) values of 0.25 and 0.86 ppb, respectively. The plausible sensing mechanism is attributed to the charge-transfer process and hydrogen bonding between the NH functional group present in nCOPA and NH 3 gas molecules, which alters the resistance of the nCOPA sensor. Based on these findings, the nCOPA sensor holds significant potential for NH 3 sensing, and its application could provide an efficient method for the real-time monitoring of NH 3 .