On-Chip Tailorability of Capacitive Gas Sensors Integrated with Metal-Organic Framework Films

Gas sensing technologies for smart cities require miniaturization, cost-effectiveness, low power consumption, and outstanding sensitivity and selectivity. On-chip, tailorable capacitive sensors integrated with metal-organic framework (MOF) films are presented, in which abundant coordinatively unsaturated metal sites are available for gas detection. The in situ growth of homogeneous Mg-MOF-74 films is realized with an appropriate metal-to-ligand ratio. The resultant sensors exhibit selective detection for benzene vapor and carbon dioxide (CO₂ ) at room temperature. Postsynthetic modification of Mg-MOF-74 films with ethylenediamine decreases sensitivity toward benzene but increases selectivity to CO₂ . The reduced porosity and blocked open metal sites caused by amine coordination account for a deterioration in the sensing performance for benzene (by ca. 60 %). The enhanced sensitivity for CO₂ (by ca. 25 %) stems from a tailored amine-CO₂ interaction. This study demonstrates the feasibility of tuning gas sensing properties by adjusting MOF-analyte interactions, thereby offering new perspectives for the development of MOF-based sensors.