The Emergence and Evolution of Borophene

Neighboring carbon and sandwiched between non‐metals and metals in the periodic table of the elements, boron is one of the most chemically and physically versatile elements, and can be manipulated to form dimensionally low planar structures (borophene) with intriguing properties. Herein, the theoretical research and experimental developments in the synthesis of borophene, as well as its excellent properties and application in many fields, are reviewed. The decade‐long effort toward understanding the size‐dependent structures of boron clusters and the theory‐directed synthesis of borophene, including bottom‐up approaches based on different foundations, as well as up‐down approaches with different exfoliation modes, and the key factors influencing the synthetic effects, are comprehensively summarized. Owing to its excellent chemical, electronic, mechanical, and thermal properties, borophene has shown great promise in supercapacitor, battery, hydrogen‐storage, and biomedical applications. Furthermore, borophene nanoplatforms used in various biomedical applications, such as bioimaging, drug delivery, and photonic therapy, are highlighted. Finally, research progress, challenges, and perspectives for the future development of borophene in large‐scale production and other prospective applications are discussed. The successful theoretical‐research‐guided synthesis of borophene marks a milestone for the synthesis of 2D materials without layered bulk structures. The excellent properties and wide applications of borophene make it a new cousin of graphene in the family of 2D materials.