Ultra-effective room temperature gas discrimination based on monolithic Pd@MOF-derived porous nanocomposites: an exclusive scheme with photoexcitation

Abstract

Chemiresistive sensing materials capable of efficiently identifying specific flammable gases are imperative. Although plenty of high-performance chemiresistive sensors have been developed in related fields, the high selectivity response to a single flammable gas at room temperature is still a great challenge. Conventional single chemiresistive metal oxide semiconductor materials exhibit similar response characteristics to flammable gases at high temperatures, while arrays are limited by high cost and miniaturization. Herein, the unique gas discrimination based on a monolithic MOF-derived chemiresistive sensor is achieved with photoexcitation at room temperature. 5.0Pd@ZnO exhibits a typical p-type semiconductor response (200 ppm, 52.89) to H₂, while it displays a typical n-type semiconductor response to other flammable gases (CO, MeOH, EtOH, and H₂S response of −25.15, −13.63, −49.92, and −40.36, respectively), which indicates that H₂ can be fully identified merely from the original electrical signal. Meanwhile, the as-prepared sensors combined the advantages of MOF and MOS materials, and exhibited high linearity response, favorable repeatability, and long-term stability. The special response characteristics of the sensor to each flammable gas have been explored in detail, and the distinct effects of two different Pd surface states on gas molecules are discovered by DFT calculations. The mechanism of the high-selectivity response behavior at room temperature is systematically analyzed. This work provides a solid reference and feasible solution for the development of high-selectivity room temperature sensors.