An in-situ FTIR-LCR meter technique to study the sensing mechanism of MnO2@ZIF-8/CNPs and a direct relationship between the sensitivity of the sensors and the rate of surface reaction

•MnO2@ZIF-8 particles are prepared using sol–gel method and while carbon nanoparticles are prepared via pyrolysis of lighthouse candle.•The detection of diethylamine vapour using MnO2@ZIF-8/CNPs composite solid state gas sensor operating at room temperature.•The gas sensor show fast-recovery time, and the sensor is insensitive to a change in humidity.•The study provides a sensing mechanism of diethylamine interaction with the prepared gas sensors using in Situ FTIR-LCR meter.