Role of covalent crosslinking and 2D nanomaterials in the fabrication of advanced organic solvent nanofiltration membranes: A review of fabrication strategies, recent advances, and challenges

Organic solvent nanofiltration (OSN) membranes have gained significant attention owing to their pivotal role in various industrial applications, including pharmaceuticals, fine chemicals, and manufacturing. This review provides a comprehensive overview of the recent advances in OSN membrane technology, focusing on membrane materials, fabrication techniques, and strategies for tuning the chemistry, structure, and performance of OSN membranes. Initially, the fundamental principles underlying OSN are described, highlighting the critical parameters influencing membrane selectivity, permeability, and stability in organic solvents. It also focuses on the importance of covalent crosslinking in the design and fabrication of dense polyamide membranes. Subsequently, the design and synthesis of novel membrane materials are discussed, including polymeric, inorganic, and hybrid membranes. The use of 2D nanomaterials is summarized, with an emphasis on their structural characteristics and tailored properties for solvent separation applications. We further explored the innovative fabrication strategies, such as interfacial polymerization, modification of ultrafiltration supports, and tuning of the active layer chemistry by incorporating the membrane structure with porous nanofillers. This review also discusses the in- homogeneity issues between inorganic nanofillers and organic matrices of membranes as well as the strategies to overcome these limitations through proper functionalization. Finally, we identified emerging trends and prospects in OSN membrane research, encompassing sustainability, scalability, and integration with other membrane processes, to address existing challenges and discover new opportunities for efficient solvent separation in diverse industrial sectors.