The exploration of two-dimensional solids is an active area of materials discovery. Research in this area has given us structures spanning graphene to dichalcogenides, and more recently 2D transition metal carbides (MXenes). One of the challenges now is to master ordering within the atomic sheets. Herein, we present a top-down, high-yield, facile route for the controlled introduction of ordered divacancies in MXenes. By designing a parent 3D atomic laminate, (Mo_2/3Sc_1/3)₂AlC, with in-plane chemical ordering, and by selectively etching the Al and Sc atoms, we show evidence for 2D Mo_1.33C sheets with ordered metal divacancies and high electrical conductivities. At ∼1,100 F cm⁻³, this 2D material exhibits a 65% higher volumetric capacitance than its counterpart, Mo₂C, with no vacancies, and one of the highest volumetric capacitance values ever reported, to the best of our knowledge. This structural design on the atomic scale may alter and expand the concept of property-tailoring of 2D materials.

Intercalated layered materials offer distinctive properties and serve as precursors for important two-dimensional (2D) materials. However, intercalation of non–van der Waals structures, which can expand the family of 2D materials, is difficult. We report a structural editing protocol for layered carbides (MAX phases) and their 2D derivatives (MXenes). Gap-opening and species-intercalating stages were respectively mediated by chemical scissors and intercalants, which created a large family of MAX phases with unconventional elements and structures, as well as MXenes with versatile terminals. The removal of terminals in MXenes with metal scissors and then the stitching of 2D carbide nanosheets with atom intercalation leads to the reconstruction of MAX phases and a family of metal-intercalated 2D carbides, both of which may drive advances in fields ranging from energy to printed electronics.

Boridene: a 2D boride: A range of two-dimensional (2D) materials, including graphene and hexagonal boron nitride, have been synthesized and studied because of the unusual properties that occur when one dimension becomes very small. MXenes are a family of materials made of layers of inorganic transition metal carbides and nitrides that are a few atoms thick and are manufactured by selective etching. Attempts to make similar boridene materials have been challenging because of the reactive nature of boride phases and because the parent materials tend to dissolve rather than selectively etch. Zhou et al . synthesized boridene in the form of single-layer 2D molybdenum boride sheets by selective etching in aqueous hydrofluoric acid to produce sheets with ordered metal vacancies, opening up an additional family of materials for study. —MSL