Gas adsorption selectivity improvement of a metal-organic framework (MOF)-based sensor presents a significant challenge. This study addresses the enhancement of gas adsorption selectivity in MOFs by introducing bimetallic centers. The bimetallic zinc/niobium MOF (Zn/Nb-NDI-BMOF) was synthesized through the solvothermal coordination of Zn and Nb metal sources with the 1,4,5,8-naphthalene tetracarboxydiimide (NDI) organic ligand. Zn/Nb-NDI-BMOF formed a hexagonal-platelet structure with a high refractive index and optical transparency after 5 h of solvothermal growth. In comparison to Zn-NDI-MOF and Nb-NDI-MOF, the developed Zn/Nb-NDI-BMOF film displayed a unique response to H2S in the presence of SO2, NO2, CO2, and HCl gases when incorporated into an optical waveguide sensor (OWGS). The enhancement in the gas-sensing selectivity of Zn/Nb-NDI-BMOF can be attributed to the bimetallic synergistic effect, which alters the framework structure and pore sizes and consequently modifies the optical configuration and activity. Upon exposure to H2S, it is susceptible to proton transfer between H2S and Zn/Nb-NDI-BMOF. Features such as a fast response (response time less than 2 s), a wide detection range (100 ppm to 1 ppb), good reproducibility, a low detection limit (0.69 ppb), thermal stability, and humidity resistance of the Zn/Nb-NDI-BMOF film OWGS for H2S make it a promising candidate for potential applications in environmental monitoring and food freshness assessment.
Nizamidin et al. (Mon,) studied this question.