Fabry–Pérot Cavity Based on Metal–Organic Framework/Graphene Oxide Heterostructure Membranes for Humidity Sensing

This paper reports a Fabry–Pérot (F–P) cavity constructed of heterostructure membranes by metal–organic framework 801 (MOF-801) and graphene oxide (GO) that can achieve high-performance relative humidity (RH) sensing. The reflectance spectrum of the cavity is tuned by adjusting the concentration of MOF-801, spin coating period, and spin coating speed to achieve the optimal reflection waveform. The humidity sensing performance of the MOF-801 membrane and MOF-801/GO heterostructure membrane F–P cavities were investigated systematically. MOF-801/GO heterostructure membranes show higher humidity sensitivity (0.32 nm/% RH) and lower detection limit (0.31% RH) comparing with MOF-801 membranes because the multifunctional reactive groups of GO can interact with H2O, which enhances adsorption of H2O. The MOF-801/GO heterostructure membrane F–P cavity shows a fast optical response (400 ms), with a maximum response value of 27.9 nm (Δλ) at 90% RH. Moreover, the MOF-801/GO heterostructure membrane cavity exhibits excellent selectivity for H2O vapor among four interfering gases of CO2, N2, He, and Ar. Meanwhile, the cavity keeps exceptional repeatability and reliability at different RH values. The sensitivity of the MOF-801/GO heterostructure membrane F–P cavity under mouth breathing is excellent, indicating the cavity is a promising candidate for human respiratory monitoring. The F–P cavity based on MOF-801/GO heterostructure membranes provides a path to fabricate high-performance real-time monitoring of humidity sensors.