Thin-film composite membranes for efficient CO2 capture: Evaluation of different polymer substrate selection strategies

Abstract

Membrane-based separation stands as a critical technological pathway toward achieving global carbon neutrality, offering a promising alternative to traditional energy-intensive CO2 capture processes. While extensive research efforts have been devoted to the molecular design of high-performance selective layers, the role of the polymer substrate-a foundational component governing mechanical integrity, transport resistance, and interfacial morphology-has remained underexplored and often overlooked. This review provides a comprehensive analysis and critical evaluation of polymer substrate selection strategies for composite membranes in CO2 separation applications. We systematically examine widely employed substrates including polysulfones (PSF, PES, PPSU), polyvinylidene fluoride (PVDF), and polyacrylonitrile (PAN), as well as emerging candidates such as polyetherimide (PEI), polyimide (PI), and polytetrafluoroethylene (PTFE). For each polymer, we detail its applications, modifications, and performance in CO2 capture processes, comparing its inherent advantages and limitations. Furthermore, we experimentally characterize the gas permeation properties of several commercial substrates to offer a practical performance benchmark. Our analysis concludes that an optimal substrate choice must adhere to a "selection-ondemand" principle, meticulously balancing application conditions, separation requirements, and cost. Finally, we identify key challenges-including interfacial compatibility, limited synergy in separation functionality, and the need for greener fabrication processes-and propose future directions for developing next-generation substrates. This work aims to establish a foundational framework for the rational selection and innovation of substrate materials, bridging the gap between academic research and industrial implementation in next-generation CO2 capture technologies.