A silver nanoparticle-anchored UiO-66(Zr) metal–organic framework (MOF)-based capacitive H2S gas sensor

Abstract

Hydrogen sulfide (H₂S) is a highly poisonous gas; if present in a workplace, it must be identified immediately at concentrations greater than 10 ppm. Although there are numerous reports on sensing H₂S gas using various techniques and approaches, there still exists a gap in terms of the limit of detection (LOD) and feasibility. In this work, we demonstrated capacitive H₂S sensing for the first time using metal–organic frameworks (MOFs) decorated with silver oxide (Ag₂O) nanoparticles as the sensing materials. The nanoparticles were deposited on three MOFs (UiO-66(Zr) BDC, UiO-66(Zr) BDC-NO₂, and UiO-66(Zr) BDC-N₃) using the impregnation technique. The sensing materials were characterized for morphology using X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy techniques. The synthesized MOFs were coated on interdigitated electrode capacitors as the dielectric materials and a comparison of their sensing properties was presented; among them, UiO-66(Zr) BDC-NO₂ loaded with Ag₂O showed the highest sensitivity towards H₂S. The optimized MOF–Ag₂O composite demonstrated experimental LOD of 1 ppm of H₂S at room temperature, showing high chemical absorption affinity towards H₂S. The work presented here is promising for developing sensitive H₂S sensors and in addition paves the way to explore and develop other possible MOF-based composite materials for gas sensing applications.