A Critical Review of Materials Enhancing the Performance of Polymer Membranes for Membrane Distillation of Saline Water

Membrane distillation (MD) is an attractive complementary technology to conventional desalination systems. Yet commercial uptake remains limited by membrane pore wetting, temperature polarisation, and material trade-offs. This review critically examines polymeric membranes and demonstrates that reported performance gains cannot be attributed to individual polymers or fillers alone, but rather to optimised structure–property interactions governing wetting resistance, mass transfer, and mechanical integrity. Through a comparative analysis of benchmark metrics (water flux, contact angle, and liquid entry pressure), we identify recurring failure mechanisms, including nanoparticle agglomeration, coating instability, and hydrophobicity-driven compromises in liquid entry pressure and durability. Moving beyond a descriptive summary of materials, this review introduces a predictive structure–property–performance framework that systematically links dominant operational limitations and targeted modification strategies. The analysis reveals that surface-localised, adhesion-controlled modifications outperform bulk approaches by preserving pore architecture while mitigating fouling and wetting risks. Key research priorities include validation under high-salinity conditions relevant to brine management, standardised environmental and leaching assessments of nanomaterials, scalable fabrication protocols supported by techno-economic considerations, and developments on bioinspired materials. By shifting focus from material novelty toward rational design principles, this review establishes actionable selection criteria to accelerate the translation of MD membranes from laboratory concepts to industrially viable desalination technologies.