Advances in poly(phenylene oxide) (PPO)-based membranes for desalination, energy, and gas separation

Poly(phenylene oxide) (PPO)-based membranes are increasingly recognized as a versatile platform for water, energy, and gas separation owing to their chemical robustness, high thermal and oxidative stability, and ease of functionalization. These attributes have enabled advances in desalination and water purification, electrochemical energy conversion and storage, and selective gas separation, positioning PPO as a strong candidate for integrated membrane solutions addressing sustainability challenges. Despite this versatility, research remains fragmented, with limited integration of performance data and design strategies across application domains. No comprehensive review has yet examined PPO membranes through a unified framework encompassing fundamental principles, modification strategies, and cross-sectoral performance metrics. This review bridges that gap by critically analyzing PPO-based membranes for interconnected separation systems. Key chemical structures, functionalization methods, and modification routes are assessed in a uniform context to reveal design-performance relationships. Sector-specific performance metrics are systematically reviewed for water electrolysis, fuel cells, batteries, electrodialysis desalination, and gas purification. Challenges, including chemical stability, dimensional control, interfacial compatibility, and durability, are examined in detail. Finally, the future research priorities are outlined to guide the development of next-generation PPO membranes with multifunctional, scalable, and circular capabilities. By consolidating knowledge across water, energy, and gas separation, this review provides a foundation for advancing PPO-based membranes as integrated solutions for sustainable and decentralized resource systems.