New improved metal-organic frameworks using dual metal centers: A novel H₂S gas sensing capability through synergistic interactions

This study explores the hydrogen sulfide (H₂S) sensing capabilities of mono- and bi-metallic metal–organic frameworks (MMOFs and BMOFs), emphasizing central-metal effects, porosity, electrochemical behavior, and sensor performance. Two MMOFs, MIL-100(Fe) and HKUST-1(Cu), were synthesized at room temperature, whereas the BMOF MOF-919 (Fe-Cu) was prepared at 100°C. FTIR, XRD, XPS, and SEM confirmed their structures, and BET analysis revealed surface areas of 1342.3 m²/g (MIL-100), 719.4 m²/g (HKUST-1), and 1461.1 m²/g (MOF-919) with pore sizes of 2.3, 5.0, and 3.1 nm, respectively. Cyclic voltammetry showed that HKUST-1(Cu) has greater electrochemical activity than MIL-100(Fe), despite its lower surface area, and that MOF-919(Fe-Cu) exhibits the largest CV response, reflecting synergistic dual-metal effects. Gas sensing tests at room temperature yielded responses of 562.7 % (MIL-100), 657.1 % (HKUST-1), and 931.6 % (MOF-919) to 10 H₂S; limits of detection were 0.43, 0.47, and 0.31 ppm, respectively. Selectivity tests against NH₃, CO, and NO₂ showed a higher response to H₂S for MOF-919, and mixed-gas experiments confirmed minimal interference. MOF-919 also demonstrated excellent repeatability and long-term stability. Theoretical calculations, including density functional theory (DFT) and adsorption energy analyses, provided further evidence for the superior performance of bi-metallic MOF-919(Fe-Cu), highlighting its enhanced adsorption capabilities and interaction with H₂S molecules. These results indicate that combining high surface area, optimal pore architecture, and bimetallic synergy can achieve superior, room-temperature H₂S sensing with rapid, stable, and reproducible performance.