Mixed matrix membranes (MMMs) have emerged as an attractive category of nanofiltration (NF) membranes, offering a promising solution to address the intrinsic trade-off that exist between permeability and selectivity in conventional polymeric membranes. This review article aims to comprehensively discuss advances reported over the past 5–10 years achieved in the field of MMMs and critically analyzes the mechanisms through which a diversity of additives affects nanofiltration behavior. The discussed researches primarily address the separation of target solutes including salts, dyes, pharmaceuticals, and heavy metals, with primary applications in water treatment and wastewater reuse. Particular emphasis is placed not only on material design but also on interfacial compatibility, performance limitations, and the permeability-selectivity trade-off. Advanced inorganic fillers, such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and MXenes, have attracted many attentions because of providing special architecture, great specific surface area, and ability to give selective transport pathways. Traditional inorganic fillers (TiO₂, ZnO, SiO₂, halloysite nanotubes, Fe₃O₄, and ZrO₂), carbon-based materials (including graphene derivatives, carbon nanotubes, and graphitic carbon nitride), and organic fillers (such as porous organic cages (POCs), and β-cyclodextrin) are comparatively discussed in terms of their merits and practical restrictions. This review indicates the relationships existing between structure, properties, and performance in various MMM designs, and provides some suggestions for future research directions. Beyond performance enhancement, this review discusses trade-offs between permeability and selectivity, filler dispersion challenges, interfacial defects, long-term stability concerns, and scalability constraints that may hinder practical implementation. The eventual aim is to develop the next generation of nanofiltration mixed matrix membranes possessing high efficiency, improved selectivity, and long-term stability.

Graphical abstract

This is a visual representation of the abstract.