A Designed ZnO@ZIF-8 Core-Shell Nanorod Film as a Gas Sensor with Excellent Selectivity for H₂ over CO

The development of H₂ gas sensors is important for H₂ production as a fuel. In this work, a ZnO@ZIF-8 core-shell nanorod film is designed and synthesized as a gas sensor through a facile solution deposition process. This film shows an excellent selective response for H₂ over CO. By fine-tuning the reaction conditions, a ZnO@ZIF-8 core-shell structure with a thin, fine-grain, porous ZIF-8 shell is obtained. Owing to the facile H₂ penetration through the ZIF-8 thin shell (≈110 nm) and the increased oxygen vacancies for the complex film, the ZnO@ZIF-8 nanorod film shows a higher H₂ sensitivity than a raw ZnO nanorod film. More importantly, the ZnO@ZIF-8 nanorod film shows no response for CO at 200 °C. Because of the fine-grain confinement of the porous ZIF-8 shell (<140 nm), the molecular sieving effect is strengthened, which allows the effective separation of H₂ over CO. This work provides a promising strategy for the design of high-performance H₂ sensors.