Future roadmap on nonmetal-based 2D ultrathin nanomaterials for photocatalysis.

• The characteristics of BP, h-BN, g-C 3 N 4 , graphene, and COFs are introduced. • The recent advances in element doping and heterojunction constructing are reviewed. • Organic amendment, hydroxyl modification, and dye sensitization are introduced. • The applications in HER, CO 2 RR, NRR, OER, and ORR are concluded. Semiconductor photocatalysis has been recognized as a feasible strategy for effective utilization of solar power to alleviate the energy shortage and environmental crisis. Efficient photocatalytic process over two dimensional (2D) ultrathin nanomaterial is one of the most paramount technologies for solving these problems. In this review, we begin with a brief introduction of five nonmetal-based 2D ultrathin nanomaterials (including black phosphorus (BP), hexagonal boron nitride (h-BN), covalent organic frameworks (COFs), graphene, and polymeric graphitic carbon nitride (g-C 3 N 4)), which mainly discusses the special characteristics of these materials. And then, as the main content of the article, recent advances of optimizing strategies for these five 2D materials are reviewed from the aspects of element doping and construction of heterojunction. We subsequently discuss the new strategies that may be effective for future optimization. Furthermore, the applications of nonmetal-based 2D photocatalysts in energy such as H 2 evolution, CO 2 reduction, N 2 fixation, O 2 evolution, and O 2 reduction are concluded. Finally, conclusions and outlooks are given for future potential directions. [ABSTRACT FROM AUTHOR]