TFC membranes are fabricated via an interfacial polymerization (IP) process involving two monomers: an amine such as m-phenylenediamine (MPD), piperazine (PIP) and phenylenediamine (PPD) dissolved in an aqueous solution; and a polyfunctional acid chloride such as trimesoyl chloride (TMC) dissolved in an organic solvent. [11] As shown in Figure 1a, a common configuration of TFC membranes includes: 1) a top ultrathin skin polyamide (PA) layer (200 nm) which controls the separation performance; 2) a middle porous support layer (60 µm) which provides the necessary mechanical support and functions as a platform for IP process; and 3) a bottom nonwoven fabric layer (100 µm) which gives further mechanical support. [12] With the advantages of this structure, TFC membranes can achieve efficient separation while maintaining mechanical strength.Despite its wide applications, TFC membranes are still facing many challenges, particularly, the trade-off between the water permeability and the solute rejection in PA films. [13] The latest review in 2019 presented a more accurate upper bound of polymer TFC membranes through analyzing more than 300 TFC-related studies, as shown in Figure 1b. [14] Based on the solution-diffusion mechanism of the TFC membranes, an increase of water permeance would inevitably lead to a decrease of solute rejection. There is an ultimate limit for the development of traditional polymer TFC membranes. Moreover, membrane fouling and chlorination pose constant challenges in the application of polymer TFC membranes. However, the demand for freshwater in human society seems bottomless, and thus high-performance TFC membranes are required.Integrating nanomaterials into the polymer TFC membranes to form TFN membranes has been identified as a promising technique to solve the drawbacks of TFC membranes. In 2007, Hoek and co-workers [15] originally developed a thinfilm nanocomposite (TFN) membrane by adding NaA zeolite into the PA matrix. Afterward, various advanced nanomaterials, carbon nanotubes, [16,17] zeolite, [15][16][17][18][19] inorganic nanoparticles, [20,21] zeolitic imidazolate framework, [22,23] metal-organic framework, [24] and so on have been incorporated with TFC membranes. Particularly, the 2D forms of these nanomaterials are believed to be excellent candidates for fabricating high-performance TFN membranes. This work is to make an exhaustive examination of current research on 2D materials Membrane-based separation technologies are essential in the fields of desalination and wastewater treatment. 2D material based thin-film nanocomposite (2D-M-TFN) membranes are emerging technology that combines 2D nanomaterials and conventional thin-film composite membranes. It has great potential to further improve the efficiency of the membrane separation process. Although extensive studies are reported, 2D-M-TFN membranes for water treatment are not systemically reviewed. This work gives an intensive summary of this emerging technology. The function, mechanisms, and common characteristics of various 2D materia...