Engineering defective organic–inorganic heterojunctions as an alternative approach to precious metal modification in ultrasensitive H2S gas detection at room temperature

The detection of low-concentration hydrogen sulfide (H2S) under mild conditions is of high research value. In this work, a Z-scheme organic-inorganic interface heterojunction was successfully fabricated using a metal-organic frameworks (MOFs, UiO-66-NH2(Zr) used in this study)-modified TiO2 nanotube array (TiNT). Instead of the high-cost precious metal (PM) modification, defect engineering (DE) was employed to enhance the H2S sensing performance. As the band structure could trigger electron transfer to the surface of semiconductors via well-known "skin effects", the increasing number of surface electrons resulted in the generation of more O2– species and thus an enhanced gas sensing response. Benefitting from the amino groups in the mesoporous structure of Zr-MOF, the as-formed gas sensor showed a strong and specific response (31 at 10 ppm) and a sub-parts-per-billion detection limit (0.55 ppb) for H2S sensing, as well as a remarkable working stability (RSD<3.6 % for 30-day operation). Furthermore, the good mechanical stability, compact size, and more environmentally friendly power supply endow the proposed gas sensors with great application potential in important fields such as wearable devices.