Vacancy Engineering for Tuning Electron and Phonon Structures of Two-Dimensional Materials

2D inorganic materials are now breeding a wide-ranging series of energy applications including catalysis, electrochemical activity, thermoelectricity and spin electronic devices. However, the physicochemical property of virgin 2D inorganic materials can scarcely satisfy the modern increasing diversificated demand of theory and applcations. In this regard, confined electron and phonon structures will be a directive for rationally tuning the intrinsic properties of 2D inorganic materials. Given this, vacancies in even infinitesimal concentrations could unlock the huge potential that exists for manipulating the energy band structure, carrier concentration, spin nature and phonon vibration and migration, which in turn will lead to the functionalization of intrinsic properties, particular in atom-thick 2D solids. The concept of vacancy regulation embodies the design philosophy of less is more, and provides an opportunity to explore uncharted quantum phenomenon. In this review, recent progress in the design of appropriate vacancies on the 2D plane, particularly from the authors' own laboratories, is summarized, and the vacancy regulation rules of electron and phonon behavior are explained. Finally, based on an unambiguous understanding of the structure-property relationships between the vacancy, electron-phonon behavior, and the intrinsic properties, future possibilities for the rational design of vacancies to acquire desirable properties are explored.