Selective Detection of Aromatic VOCs by Monolayer Ti ₂ CO ₂ MXene: A First-Principles Study

Volatile organic compounds (VOCs), particularly aromatic pollutants such as benzene and toluene, pose severe environmental and health risks, necessitating the development of highly selective and sensitive gas sensors. Here, we systematically investigate Ti2CO2 as a chemiresistive sensor for five representative VOCs (benzene, toluene, methanol, ethanol, and acetone) using first-principles calculations and Boltzmann transport theory. Ti2CO2 exhibits strong adsorption affinity and remarkable selectivity toward benzene and toluene, with adsorption energies of −0.615 and −0.725 eV, respectively. This selectivity originates from strong π–p orbital hybridization and feedback interactions with O-2p states. Charge transfer and density of states analyses confirm the formation of impurity states near the Fermi level, effectively modulating electronic and transport properties. Notably, benzene and toluene show favorable recovery times (2.15 × 10–2 s and 1.51 s) and significant sensing responses under both hole- and electron-dominated conduction. Upon adsorption, hole conductivity decreases while electron conductivity increases, consistent with a charge-transfer-driven sensing mechanism. The sensing responses reach −72.53 and −53.49% for benzene and toluene under hole-dominated conduction and 41.98 and 221.14% under electron-dominated conduction. These results establish Ti2CO2 as a promising platform for room-temperature, high-performance VOC detection, particularly for aromatic gases, and provide insights for designing next-generation MXene-based sensors.