MXenes and other 2D nanosheets for modification of polyamide thin film nanocomposite membranes for desalination

• Critical review on 2D nanosheets incorporated- and interlayered-polyamide membranes. • Recent advances in fabrication of nanosheets-modified polyamide TFNs and ITFNs. • Comparison of various 2D nanosheets introduced into the structure of PA membranes. • Describing the transport mechanisms in TFNs and ITFNs. • Required outlooks and efforts for development of TFNs and ITFNs. Thin film composite (TFC) membranes have been serving as benchmark membranes for water treatment and desalination. Fabrication of such composite membranes is still based on the conventional interfacial polymerization process at the boundary layer of two immiscible phases, i.e., an aqueous phase and an organic phase. Among numerous nanoparticles used into the structure of thin film nanocomposite (TFN) membranes, two-dimensional (2D) nanosheets such as graphene oxide (GO), 2D metal–organic framework (MOF), boron nitride (h-BN), carbon nitride (g-C 3 N 4 ), molybdenum disulfide (MoS 2 ), and MXenes have gained considerable attraction to improve the performance and morphology of fabricated TFN membranes. Such 2D nanosheets significantly exhibited high specific area, huge amounts of terminations, and high and fast adsorption properties. This review is a leading article to critically and exclusively study the introduction of MXenes and other 2D nanosheets into the structure of polyamide thin film membranes for desalination. MXenes illustrated highly surface area, strong adhesion properties, desired electrical and thermal conductivity, mechanical stability, flexibility, as well as optimal dispersibility and hydrophilicity which make them wonderful candidates to improve the efficiency of 2D-embedded polyamide membranes. Intercalated and interlayered thin film nanocomposite (ITFN) membranes as a new class of TFN membranes, which nanomaterials are sandwiched between the top polyamide layer and the underneath substrate, were critically reviewed as well. In fact, this review has critically studied the 2D nanosheet-included TFN membranes in two separate sections including TFN and ITFN membranes. Different transport mechanisms such as gutter effect and tortuous path theory have been discussed as well.