Selective ethanol vapour sensing enabled by amine-functionalized MOF–polyetherimide hybrid membranes

Abstract

A hybrid polymeric membrane for ethanol gas sensing was fabricated via a facile solution-casting approach by incorporating MOF-71 and amine-functionalized MOF-71 (NH₂-MOF-71) nanoparticles into a polyetherimide (PEI) matrix. The resulting PEI/MOF-71 and PEI/NH₂-MOF-71 composite membranes were systematically characterised using Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, and N₂ adsorption–desorption isotherms to evaluate chemical interactions, thermal stability, morphology, elemental distribution, and porosity. The incorporation of MOF-71 and NH₂-MOF-71 enhanced membrane porosity, surface area, and gas diffusivity, leading to improved sensing performance. Notably, the PEI/NH₂-MOF-71 membrane exhibited superior sensitivity and selectivity toward ethanol vapour, with detectable responses at concentrations as low as 25 ppm under ambient conditions and a calculated limit of detection of approximately 8–12 ppm. Rapid and reproducible response and recovery times of approximately 300 s and 360 s were achieved at ethanol concentrations of 100–125 ppm. The enhanced sensing performance is attributed to the presence of amine functional groups, which promote stronger ethanol adsorption through hydrogen bonding and dipole–dipole interactions. These results demonstrate that NH₂-MOF-71/PEI composite membranes provide a simple and effective platform for room-temperature, ppm-level ethanol detection with potential applications in industrial safety and environmental monitoring.