Low-concentration CO₂ capture system with liquid-like adsorbent based on monoethanolamine for low energy consumption

Direct air capture (DAC) of atmospheric CO₂ is becoming ever more important for a carbon neutral society. To achieve this, it is critical to reduce the energy consumption of DAC systems. In this work, as a solution, a liquid-like adsorbent (LLA) is used as an adsorbent for DAC of low-concentration CO₂. We improve the performance of LLA with monoethanolamine (MEA), and named it as LLA-M to efficiently capture atmospheric CO₂ and reduce energy consumption at DAC environment. The effective dispersion of MEA in the LLA promotes CO₂ capture by overcoming their low thermal stability. When 40 wt% MEA is added, the highest performance is achieved along with a CO₂ capture capacity of 2.50 mmol g⁻¹ in 100% CO₂ atmosphere and 1.01 mmol g⁻¹ in low CO₂ concentration atmosphere. The loss and deterioration of MEA is suppressed by the LLA and therefore the performance is stably maintained while repeating the CO₂ capture/regeneration cycles. Consequently, the CO₂ capture capacity is improved by 29.9% compared with when using only MEA. More importantly, the results indicate a record CO₂ capture energy consumption of 0.89 GJ t_CO2⁻¹ at 100% CO₂ condition and 2.13 GJ t_CO2⁻¹ at 400 ppm CO₂ condition. Furthermore, the LLA-M can be recycled below 120 °C which makes it possible to reduce energy consumption by exploiting renewable energies such as solar heat. This study offers a promising low-carbon route for efficient atmospheric CO₂ capture using an LLA incorporated with MEA.