▎ 摘　　要

As a two-dimensional (2D) giant polycyclic aromatic molecule, graphene provides a great opportunity for studying the behaviors of chemical reactions in two dimensions. However, the chemistry of graphene is challenging because of its extreme inertness due to the highly delocalized pi electron system. Recently, photogenerated free radicals have been demonstrated to effectively activate the chemical reactions of graphene. Such kinds of graphene photochemistry provide a new route for the covalent functionalization and band structure engineering of zero-gap graphene. In this chapter, the graphene photochemistry based on photogenerated free radicals is reviewed, including photohalogenation, photoarylation, photoalkylation, and photocatalytic oxidation. Although most photochemical reactions on graphene can be inspired by its small organic analogues, graphene photochemistry is of particular attraction due to its infinite 2D geometry, which offers a platform for studying geometry-correlated covalent chemistry, including single-and double-sided covalent addition reactions, asymmetric chemistry on two faces of monolayer graphene, edge-selective chemistry, and interlayer coupling-dependent few-layer graphene chemistry. In addition to the modulation of surface properties and the band structure engineering, new 2D derivatives and superlattices with fascinating features beyond mother graphene can be built by graphene photochemistry, which greatly expands the graphene family and its attraction. This chapter also summarizes the potential applications of graphene photochemistry with a specific focus being laid on the general consideration and understanding of graphene photochemistry towards electronic/optoelectronic devices and materials science. At the end, a brief discussion on the future directions, challenges, and opportunities in this emerging area is provided.