Near‑Zero Energy CO2 Capture Using Vapour Assisted Phase Swing Adsorption (VAPSA)

Microporous materials are promising adsorbents for gas separations, but their adoption has been limited by the energy requirements of vacuum or heat used to regenerate the material. Lower energy swing triggers have been explored (such as light, magnetism, electricity, and humidity) to desorb gases; however, these alternative processes can also use large amounts of energy at scale. Hydrogen bonded organic frameworks (HOFs) are molecular microporous materials that exhibit solution processibility and polymorphism. We show that a HOF, MeTBAP‑α, can switch between its porous crystalline α‑phase and a dense, non‑porous salt phase via deprotonation with amine vapour. This process is then reversed via alcohol exposure. By cycling between these porous and non‑porous states, we demonstrate a vapour assisted phase swing adsorption (VAPSA) process where CO2 can be repeatedly adsorbed and desorbed. VAPSA is unique in requiring near‑zero direct energy input, paving the way to gas separations with dramatically reduced energy footprints.