Semiconducting Mesoporous MOF/Metal Oxide Heterostructures for Enhanced Gas Sensing.

Metal-organic frameworks (MOFs) show great potential in molecular sensing devices due to their precise microporous structure and high specific surface area. However, their performance is hindered due to poor conductivity and low mass transfer efficiency within micropores. In this study, semiconducting mesoporous MOF/metal oxide (mMOF/MO) heterostructures (e.g., mZIF-8/ZnO, mUiO‒66/CeO2) were prepared by precise in situ surface oxidation. The semiconducting mMOFs/MOs possess enhanced conductivity contributed by metal oxides, high mass transfer efficiency enhanced by the mesoporous structure, and high specific surface area brought by the microporous structure. The mZIF-8/ZnO exhibited high sensitivity to low-concentration NO2 (S = 1385% @ 10 ppm) at a low working temperature (145 °C), with high selectivity (SNO2/Sgas >4), fast response speed (40 s), and low limit of detection (LOD) (67 ppb). Similarly, the semiconducting mUiO‒66/CeO2 heterostructure showed enhanced sensing performance toward NH3, demonstrating the universality of this strategy for constructing mMOF/MO heterostructure semiconductor materials. This work paves a way for endowing MOFs with conductivity and mesopores for various applications including electronic devices and heterogeneous catalysis.