MOF-derived CdS@c/h-In2O3 hollow hexagonal prism with surface-grown nanofibers for ppb-level formaldehyde detection: an insight into synergistic enhancement of endogenous phase-homojunction and heterojunction

Detection of ppb-level formaldehyde at low temperatures is a great pursuit for metal oxide semiconductor sensors. To realize this goal, metal organic framework (MOF) derived hollow hexagonal prism with surface-grown nanofibers were successfully prepared and modified using quantum dots, affording a 3D/0D heterojunction with excellent sensing performance. The CdS@c/h-In2O3-2 hollow hexagonal prism exhibits outstanding sensing properties (107.37 for 100 ppm), ideal selectivity, and low detection limit (160 ppb) at 160 °C. Moreover, the possible formation mechanism of the hollow hexagonal prism and endogenous phase-homojunction are proposed. Further, an insight into the synergistic enhancement of endogenous phase-homojunction and heterojunction is presented, including the gas diffusion, density functional theory (DFT) calculations, and resistance-controlled mechanism. The distinguished HCHO-sensing performance can be attributed to MOF-derived endogenous phase-homojunction, 3D/0D heterostructure, hollow morphology, and confined internal space, which ultimately synergize to strengthen the adsorption and electron transfer behavior of oxygen and HCHO molecules. Overall, this work provides new insights into the feasible strategy and theoretical viewpoint concerning high-performance HCHO sensors. [Display omitted] •A promising 3D/0D hollow hexagonal prism decorated with QDs were prepared.•The CdS@c/h-In2O3 exhibits excellent sensing behavior towards ppb-level HCHO.•An insight into synergistic enhancement of phase-homojunction and heterojunction is shown.•DFT revealed the adsorption behavior and electron transfer characteristics.•Homojunction, heterojunction and hollow morphology enhance performance.