Extending the MXenes to MOenes with Emergent Quantum Phenomena

MOenes, as emerging MXenes-like materials, have garnered significant attention due to their fantastic properties and promising applications. However, MOenes have rich structural spaces, and most of their intrinsic characters are still unknown, which severely limit their further exploration in certain areas. In this work, using first-principles and high-throughput calculations, we systemically explore the MOenes family by varying the "M" and "O" sites from the aspect of their mechanical and kinetic stability as well as electronic traits. A database search (http://moenes.online) unveils 464 stable MOenes materials, of which we highlight 1T-Y₂OF₂ and 2H-Ti₂SF₂/2H-Ti₂SeF₂ are topological MOenes with an ideal two-dimensional Dirac nodal loop or edge states and 14 direct semiconductors with the wide light-harvesting ability ranging from the ultraviolet to near-infrared region. Specifically, single layer 2H- and 1T-Y₂TeO₂ have long carrier lifetimes of 2.38 and 1.24 ns, respectively. In addition, the 2H-Zr₂O(O)₂ monolayer shows a spin-valley coupling phenomenon, and the valley spin splitting is apparent and robust within conduction bands. These appealing features make the MOenes family suitable for next-generation electronic devices.