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 H 2 O, which enhances adsorption of H 2 O. 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 H 2 O vapor among four interfering gases of CO 2, N 2, 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.