Optimizing CO₂ Adsorption/Desorption via the Coupling of Imidazole and Carbon Nanotubes Paper for Spontaneous CO₂ Uptake from Ambient Air and Solar-Driven Release

Direct air capture (DAC) is a sustainable technology to alleviate the greenhouse effect and a reliable pathway to acquire inexhaustible CO2 for the production of costly chemicals and energy products. Current DAC technologies with amine-related sorbents rely on chemisorption, while they consume intensive energy for CO2 release and sorbent regeneration by heating. Developing new DAC processes with weak, reversible adsorption can substantially reduce the regeneration energies. Herein, the design of CO2 breathing paper (CBP) is demonstrated toward spontaneous CO2 extraction from ambient air and solar-driven regeneration. The CBP is fabricated by coupling 2-ethyl-4-methylimidazole to carbon nanotube paper on the basis of density functional theory calculations. At ambient conditions, CBP spontaneously captures atmospheric CO2 with a capacity of 0.14-1.75 mmol g-1 at 0-35 C-degrees through non-covalent electrostatic interaction. Upon exposure to sunlight, all adsorbed CO2 can be released and converted to concentrated gas for storage. Attractively, the efficiency of solar-driven CO2 release is much higher than the traditional temperature-swing method owing to the IR sensitivity of CO2. Besides the reversibility, the mild conditions also ensure the durability of CBP. These findings suggest that the CBP is a promising candidate for cost-effective DAC.