Fast and Sensitive Detection of CO by Bi-MOF-Derived Porous InO/FeO Core-Shell Nanotubes.

InO is an optimal material for sensitive detection of carbon monoxide (CO) gas due to its low resistivity and high catalytic activity. Yet, the gas response dynamics between the CO gas molecules and the surface of InO is limited by its solid structure, resulting in a weak gas response value and sluggish electron transport. Herein, we report a strategy to synthesize porous InO/FeO core-shell nanotubes derived from In/Fe bimetallic organic frameworks. The fabricated porous InO/FeO-4 core-shell nanotubes present outstanding gas sensitivities, including a response value 3.8 times (33.7 to 200 ppm CO at 260 °C) higher than that of monometallic-derived InO (8.7), ultrashort response and recovery times (23/76 s) to 200 ppm CO, low detection limit (1 ppm), promising selectivity, and long-term stability. The enhanced sensing mechanisms are clarified by the combination of experiment and first-principles calculations, showing that the synergetic strategy of higher adsorption energy, increased electrical conductivity, higher electron transfer numbers, and larger specific surface area of porous core-shell structures promotes the surface activity and charge transfer efficiency. The present work paves a way to tune gas-sensing materials with special morphologies for the development of high-performance CO sensors.