Novel SnO2/ZnO gas-sensitive materials for high formaldehyde selectivity constructed by way of doping Sn into ZIF-8

Abstract

Formaldehyde sensors represent an effective technology for real-time, online monitoring of formaldehyde concentrations. The selectivity of gas-sensitive materials for formaldehyde is a fundamental determinant of sensor performance and is crucial for the development of formaldehyde sensing technology. In this work, Sn-doped Zn-MOFs were employed to fabricate SnO₂/ZnO micro-nano materials, and their selective response behaviors to formaldehyde were systematically explored. The results demonstrate that 5% SnO₂/ZnO, prepared with 5% Sn doping, exhibits exceptional selectivity for formaldehyde. Under testing conditions of 170 °C and relative humidity below 60%, the 5% SnO₂/ZnO sensor achieved a selectivity coefficient of 0.87 toward 50 ppm formaldehyde, with a response value of 72.8, response and recovery times of 81/30 seconds, a linear regression coefficient of 0.9997, and a minimum detection limit of 0.047 ppm. Moreover, the 5% SnO₂/ZnO sensor demonstrates excellent selectivity, anti-interference capability, and stability for formaldehyde detection. The enhanced formaldehyde selectivity is attributed to the high specific surface area, abundant pore structure, abundant oxygen vacancies, and n–n heterojunctions present in the 5% SnO₂/ZnO composite.