Understanding\nthe Intrinsic Reactivity of Black Phosphorus

ConspectusBlack phosphorus\n(BP), a rediscovered two-dimensional (2D) material,\nhas garnered significant interest due to its unique structure and\nphysicochemical characteristics, including adjustable direct bandgaps,\nhigh carrier mobility, large specific surface area, and pronounced\nchemical reactivity. Distinct from the flat atomic structure of graphene,\nBP features a puckered honeycomb-like structure derived from sp<sup>3</sup> hybridization. In addition to the three-coordination, each\nphosphorus atom possesses a lone pair of electrons, leading to an\nelectron-rich nature. A variety of nanostructures such as nanosheets,\nnanoribbons, and quantum dots are developed from the bulk crystal\nof BP. The large surface area of nano BP provides numerous reactive\nsites that augment intralayer chemical interactions. Therefore, nano\nBP serves as a versatile scaffold for materials engineering, with\npotential applications across chemistry, catalysis, energy, and biomedicine.\nIt is crucial to have a deep and systematic understanding of the hybridization\ninteractions between BP and diverse molecules or materials, which\nis essential for functional design of BP-based materials for target\napplications.Researchers have witnessed a surge in discussions\nsurrounding the\nstructure, physical properties, and synthesis methods of BP in recent\nyears. However, the intrinsic reactivity of BP has received limited\nattention. The chemical properties of BP are usually associated with\nits environmental instability or degradation, and the main efforts\nare focused on its passivation rather than its exploitation. The intrinsic\nreactivity of BP facilitates a range of emerging applications including\nbiomedicine, reducing agents, and composite construction. Notably,\nthe controllable biodegradation of BP nanosheets can inhibit tumor\ngrowth, a phenomenon that has inspired the development of “bioactive\nphospho-therapy” as a cancer treatment strategy both in vitro\nand in vivo. In this Account, we first discuss the origin of BP’s\nchemical reactivity, and then categorize the typical types of chemical\nreactions, including redox reactions, covalent bonding, and noncovalent\ninteractions. Each section is dedicated to a specific interaction\ntype and is accompanied by relevant applications. These applications,\nwhich include catalysis, ion storage, sensors, and drug delivery,\neffectively demonstrate the structure–property–function\nrelationships inherent in BP-based functional materials. Finally,\na forward-looking perspective on the reactivity of BP is presented\nin the conclusion, which attempts to address the fundamental scientific\nquestions and current technical challenges in this field. This Account\nis expected to encourage researchers to further explore the multifaceted\npotentials of BP across various areas.