Room-temperature MOF-ZnO gas sensors based on the incorporation of RE (Eu, Er) for ppb-level n-butanol sensing and DFT mechanistic investigation

Eu/Er co-doped MOF-ZnO sensor enables room-temperature n-butanol detection. • 13.88-fold enhancement over ZnO (555/40) and LOD 862.6 ppb • Response/recovery: 33/27 s; good selectivity & stability • DFT: oxygen vacancies, surface area, band structure, adsorption energy The rapid advancement of industrialization has led to the emission of a growing number of volatile organic compounds (VOCs) into the atmosphere, posing significant threats to human health and the environment. Among these, n-butanol is recognized as a particularly harmful VOC. Herein, we propose a MOF-ZnO-based gas sensor for n-butanol doped with rare earth elements (Eu, Er), synthesized via a homogeneous co-precipitation method. The as-prepared samples were comprehensively characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) analysis, and ultraviolet-visible (UV–vis) spectroscopy to evaluate their morphological, structural, and physicochemical properties. Compared with the pure MOF-ZnO and the doped MOF-ZnO individually with 0.08 wt% Eu and 0.06 wt% Er, respectively, the co-doped MOF-ZnO with 0.04 wt% Eu 0.03 wt% Er presented the highest oxygen vacancy concentration and the largest specific surface area, as well as the optimal response, selectivity, and long-term stability toward n-butanol. Notably, at room temperature, the co-doped ZnO sensor achieved the highest response value of 555 toward 100 ppm n-butanol, representing a 13.88-fold enhancement over pure MOF-ZnO (40), with a limit of detection (LOD) as low as 862.6 ppb. The sensor also displayed fast response and recovery times of 33 s and 27 s, respectively, for n-butanol detection. Furthermore, the modified energy band structure and surface adsorption energy (E ads ) of the doped product were investigated via Density Functional Theory (DFT) mechanistic calculations. These findings offer a versatile and highly promising strategy for constructing high-performance VOC sensors.