Extending the MXenes to M<b><i>O</i></b>enes with Emergent Quantum Phenomena

M<b><i>O</i></b>enes, as emerging MXenes-like materials, have garnered significant attention due to their fantastic properties and promising applications. However, M<b><i>O</i></b>enes 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 M<b><i>O</i></b>enes family by varying the "M" and "<b><i>O</i></b>" sites from the aspect of their mechanical and kinetic stability as well as electronic traits. A database search (http://moenes.online) unveils 464 stable M<b><i>O</i></b>enes materials, of which we highlight 1T-Y₂OF₂ and 2H-Ti₂SF₂/2H-Ti₂SeF₂ are topological M<b><i>O</i></b>enes 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 M<b><i>O</i></b>enes family suitable for next-generation electronic devices.