Heterostructured α‐Fe₂O₃@ZnO@ZIF‐8 Core–Shell Nanowires for a Highly Selective MEMS‐Based ppb‐Level H₂S Gas Sensor System

Highly selective and sensitive H 2 S sensors are in high demand in various fields closely related to human life. However, metal oxide semiconductors (MOSs) suffer from poor selectivity and single MOS@metal organic framework (MOF) core–shell nanocomposites are greatly limited due to the intrinsic low sensitivity of MOF shells. To simultaneously improve both selectivity and sensitivity, heterostructured α‐Fe 2 O 3 @ZnO@ZIF‐8 core–shell nanowires (NWs) are meticulously synthesized with the assistance of atomic layer deposition. The ZIF‐8 shell with regular pores and special surface functional groups is attractive for excellent selectivity and the heterostructured α‐Fe 2 O 3 @ZnO core with an additional electron depletion layer is promising with enhanced sensitivity compared to a single MOS core. As a result, the heterostructured α‐Fe 2 O 3 @ZnO@ZIF‐8 core–shell NWs achieve remarkable H 2 S sensing performance with a high response ( R air / R gas = 32.2 to 10 ppm H 2 S), superior selectivity, fast response/recovery speed (18.0/31.8 s), excellent long‐term stability (at least over 3 months), and relatively low limit of detection (down to 200 ppb) at low operating temperature of 200 °C, far beyond α‐Fe 2 O 3 @ZIF‐8 or α‐Fe 2 O 3 @ZnO core–shell NWs. Furthermore, a micro‐electromechanical system‐based H 2 S gas sensor system with low power consumption is developed, holding great application potential in smart cities.