The upsurge in population and industrialization has instigated the demand in improvement in the existing water purification systems. Numerous organic, and later inorganic materials, have showcased huge potential in different membrane separation processes. Recently, a novel range of two-dimensional (2D) materials possessing atomic thickness, high robustness, excellent mechanical stability, and even great fouling resistance have shown their appealing potential as membrane materials in this respect. The high aspect ratios of 2D materials enable the feasible control of membrane assembled structures. The membrane structure of 2D materials plays a crucial role in separation performance. Regarding the molecular transport pathway, the assembled structure is categorized into laminates and in-plane pores here. From this aspect, this review discusses the most recently progress of 2D materials membranes, including graphene-based materials, MXenes, transition metal dichalcogenides, metal organic frameworks, covalent organic frameworks, and boron nitride, in the field of water purification. According to their membrane assembled structures, the design strategies with separation mechanism and separation performance have been reviewed. Lastly, challenges and futuristic upgrades to enhance their membrane operation are discussed accordingly. This review provides a new perspective of 2D material assemblies on membrane design for advancing separation performance in water purification.