ABSTRACT: Motivated by the successful synthesis of Janus monolayers of transition metal dichalcogenides (i.e., MoSSe), we computationally investigated the structural, electronic, optical, and transport properties of functionalized Janus MXenes, namely MM'CT2 (M, M' = Zr, Ti, Hf, M ≠ M', T = -O, -F, -OH). The results of the calculations demonstrate that five stable O-terminated Janus MXenes (ZrTiCO2-I, ZrHfCO2-I, ZrHfCO2-III, HfTiCO2-I, and HfTiCO2-III), exhibit modest bandgaps of 1.37-1.94 eV, visible-light absorption (except for ZrHfCO2-I), high carrier mobility, and promising oxidization capability of photoinduced holes. Additionally, their indirect-gap, spatially separated electron-hole pairs, and the dramatic dif