Modulation of the electronic structure and oxygen vacancies in cobalt-based metal-organic frameworks induced by iron ions to enhance the sensing performance of trimethylamine

In this study, a novel gas sensor based on iron (Fe) - cobalt (Co) bimetallic metal-organic framework (MOF) was synthesized and applied to the detection of trimethylamine (TMA) for the first time. The sensing mechanism was elucidated through density functional theory (DFT) calculations. Experimental results demonstrate that the introduction of Fe 3+ into the Co-MOF (Fe/Co-MOF) not only increased its specific surface area and the number of oxygen vacancies but also enhanced the intrinsic conductivity and carrier mobility of Co-MOF, which improves the response ability for TMA detection. The response value and response/recovery time of Fe/Co-MOF to 100 ppm TMA were 164.18 and 8 s/3 s, and the minimum detectable concentration was 1 ppm at room temperature. DFT calculations revealed that the introduction of Fe 3+ will enhance the charge transfer ability of Co-MOF, making its D-band center closer to the Fermi level, thereby enhancing the electron density and reactivity of metallic active sites. By introducing Fe 3+ into Co-MOF, not only will more oxygen vacancies be generated, but also it will combine with Co 2+ to form a Fe-O-Co channel structure, thereby effectively enhancing the electronic transmission ability of the Co-MOF. The design of the Fe/Co-MOF structure has solved the problem of low conductivity of Co-MOF and has successfully been applied to the detection of TMA for the first time, providing a new strategy for the application of MOFs materials in gas detection.