An efficient and affordable NH3 sensor is
crucial for
accurately monitoring atmospheric pollution and human health. Nanoporous
covalent organic polymers (nCOPs) are promising candidates for detecting
NH3 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 (CN) to synthesize an amine (C–N)-containing
nanoporous COP (nCOPA). We have employed these as sensing materials
for detecting NH3 at 25 °C. Interestingly, the nCOPA
sensor displays an impressive 18.6 times increased response of 1700%
toward 500 ppm of NH3 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 NH3 gas molecules, which alters
the resistance of the nCOPA sensor. Based on these findings, the nCOPA
sensor holds significant potential for NH3 sensing, and
its application could provide an efficient method for the real-time
monitoring of NH3.