Diverse scenarios selective perception of H2S via cobalt sensitized MOF filter membrane coated Three-Dimensional metal oxide sensor

Abstract

Using metal–organic frameworks (MOF) materials as a filter membrane is an innovative method to improve the selectivity of gas sensors by adjusting the size of the pores and cavities; however, the active surface and dynamic sensing processes are inevitably negatively affected. A facile but effective strategy was implemented in this work by integrating Co ions as catalysts into the inner three-dimensional ZnO skeleton and outer MOF filter membrane. The appropriate incorporation of Co cations was found to increase the surface area, facilitate the adsorption of oxygen species onto the zeolitic imidazolate framework (ZIF) surface, and promote the catalytic oxidation of H2S. In the optimised gas sensor, an enhanced response of H2S (260 to 5 ppm) and a low detection limit (70 ppb) at 180 °C were obtained because of the catalytic action of appropriate amounts of Co. In addition, beyond the molecular sieve effect to exclude interference from larger gas molecules, the incorporation of Co catalysts can adjust the number of base sites in the ZIF filter (from 1.592 to 3.325 mol/g), which further assists in avoiding basic-type interference from gas molecules with smaller kinetic diameters. As a result, a 130-fold increase in H2S selectivity (among various interfering gases) and a 54-fold increase (compared to the control sensor without Co) were obtained. Moreover, the sensor was demonstrated to be a powerful platform for assessing trace amounts of H2S in pesticide volatile gas identification and protein food quality evaluation.