Selective hydrogen bonding enables solar-driven amine removal from carbon capture systems

Amine-based CO₂ capture suffers from volatile amine escape, causing atmospheric emissions, while the widely used water scrubbers for emission control produce large amounts of alkanolamine-containing wastewater (ie monoethanolamine (MEA)). However, solar-driven purification, a promising low-energy treatment for such wastewater, is challenged by amine co-evaporation. Herein, a bi-functional graphene oxide based polyvinyl alcohol aerogel (GPA) was developed for synergistic MEA capture and water evaporation with long-term stability, achieving 99.5% MEA removal and an evaporation rate of 1.36 kg m^-2 h^-1 under 1 sun illumination. Combined DFT and MD simulations reveal that hydroxyl (-OH) from the polyvinyl alcohol and carboxyl (-COOH) from graphene oxide synergistically establish selective hydrogen bonding interactions with MEA, where -COOH exhibited exceptionally long hydrogen-bond lifetimes (6.1 ps), thereby immobilizing MEA whilst also allowing rapid water diffusion. GPA maintains >95% MEA removal over 20 consecutive days and under extreme pH conditions. Life cycle assessment indicates that GPA has the lowest environmental impact among comparable systems, accounting for only 6% of global warming impact. This work resolves the amine co-evaporation bottleneck and provides a sustainable pathway to manage alkanolamine-laden wastewater from carbon capture systems.