A 3D conductive amorphous unsaturated-ligand MIL-68(Fe) MOF as room-temperature H₂S chemiresistive sensor

Simultaneously achieving chemiresistive gas sensors with high selectivity, sensitivity, and stability remains a significant challenge. In this study, inspired by the H₂S-specific catalytic enzymes in biological systems, we construct an amorphous unsaturated-ligand MIL-68(Fe) 3D MOF via in situ thermal induction. Without the introduction of extrinsic catalytic or conductive components, this MOF modification strategy creates unsaturated Fe atoms within the framework itself. These atoms function dually as catalytic and conductive sites, thereby overcoming the inherent low conductivity of conventional 3D MOFs and enabling the direct construction of chemiresistive sensor for room-temperature molecular olfactory sensing. The targeted water-adsorption-coordinated catalytic mechanism bypasses the limitations of traditional oxygen adsorption processes to achieve unprecedented comprehensive performance, including fingerprint-level selectivity (against 29 interfering gases), superior sensitivity coefficient (~83/ppm), ultra-low measured lower limit (1 ppb), rapid gas sensing response/recovery characteristics (~30 s/73 s), and excellent long-term stability at room temperature.