A review of nano-confined composite membranes fabricated inside the porous support

Asymmetric composite membranes composed of a porous support layer and compact selective layer have been used in many fields. Nowadays, most studies focus on the material design and structure optimization of the selective layer. However, nano-confined pores in the porous support layer can also be used to construct a composite membrane with unique architecture. The functional polymer and nanoporous particles can be embedded in the pores rather than on the support surface to form a composite membrane, which can solve some significant problems, such as the contradiction between integrity and ultrathin thickness of the selective layer, the interfacial adhesion between selective layer and support layer, and the orientation of the selective layer. The separation performance and the stability of the composite membranes are thus improved. Summarized in this review are the latest studies on the formation of composite membranes using confined space of porous support layer which are defined as a nano-confined composite membrane in this review, with the focus on membrane structure, pore property, and fabrication strategy. The summary and outlook are discussed with a perspective on high-performance composite membranes.