Reversible Energy Coupling Enables Direct Air Capture for Efficient CO₂ Concentration and Fuel Production

Rising atmospheric CO₂ concentrations—now exceeding 410 ppm—pose a major challenge to climate stability. While point-source carbon capture technologies have advanced, they remain confined to fixed emission sites and cannot address legacy emissions dispersed in the atmosphere. Direct air capture (DAC) offers a complementary strategy, but is constrained by the high energy costs of sorbent regeneration, especially under ambient conditions. Inspired by biological energy coupling, we developed a DAC system that thermodynamically links CO₂ binding with sorbent dissolution and release with sorbent recrystallization. Here we show that hexapodal amine sorbents, such as 2-PHA, enable efficient CO₂ capture from air at 0 °C and release at 40 °C using only mechanical stirring, with no external heating. The exothermic formation of carbamate and bicarbonate drives sorbent dissolution, effectively storing energy that is later recovered through crystallization to power CO₂ desorption. This reversible energy-coupling mechanism allows air-captured CO₂ to be enriched to >95% purity and fed directly into an electrochemical reactor. Using tailored electrocatalysts, the system converts CO₂ to CO or formate with up to 99% Faradaic efficiency; the resulting CO stream reaches 82% purity, suitable for direct ignition. This study introduces a generalizable design principle—coupling chemical capture with phase transitions—to minimize regeneration energy, offering a scalable, modular platform for atmospheric CO₂ capture and utilization.