Structure-Performance Relationships in Nanofiltration Membranes: From Molecular Architecture to Intelligent Membrane Systems

Abstract

Nanofiltration (NF) has become an indispensable platform for sustainable separations, yet its continued advancement is constrained by persistent trade-offs between permeability and selectivity, limited solute-solute discrimination, fouling susceptibility, and poor long-term stability under aggressive operating conditions. Despite rapid progress across polyamide chemistry, nanomaterial incorporation, and process modelling, the field remains fragmented, with insights confined to isolated material classes, fabrication routes, or applications, and lacking a unifying framework that connects molecular design to system-level performance. This review addresses that gap by establishing a coherent, multiscale structure–performance framework that traces a continuous mechanistic thread from molecular architecture to industrial module. We first critically examine the molecular-scale design of polyamide selective layers, questioning whether it genuinely reshapes membrane structure and introduces functional engineered nanoscale transport pathways. We then analyse morphology-performance correlations, advanced multiscale predictive modelling, and the rapidly emerging role of artificial intelligence and data-driven design in accelerating membrane discovery and optimization. Beyond material performance, we critically appraise fouling mechanisms and antifouling strategies, sustainability through life-cycle and techno-economic assessment, and the frequently underappreciated lab-to-module performance gap that governs real-world deployment. Throughout, we interrogate conflicting findings, reproducibility and scalability limitations, and the economic and environmental barriers that separate laboratory achievements from industrial reality. By integrating these traditionally siloed domains within a single critical synthesis, this review consolidates fragmented knowledge, identifies the most consequential research gaps, and articulates a scientific roadmap toward highly selective, energy-efficient, and industrially viable NF systems for global water security and sustainable resource recovery.