Development of High-Capacity and Water-Lean CO₂ Absorbents by a Concise Molecular Design Strategy through Viscosity...

The exponentially increasing viscosity of water-lean CO₂ absorbents during carbon capture processes is a critical problem for practical application, owing to its strong correlation with systems' mass transfer properties, as well as convenience of transportation. In this work, a concise strategy based on structure-viscosity relationships is proposed and applied to construct a series of functionalized ethylenediamines as single-component absorbents for post-combustion CO₂ capture. These nonaqueous absorbents have outstanding viscosities (50-200 cP, 25 °C) at their maximal CO₂ capacities (up to 22 wt % or 4.92 mol kg^-1 , 1 bar), and are readily regenerated at low temperatures (50-80 °C) under ambient pressure. Additional capture of CO₂ through physisorption could also be achieved by operating at high pressures. The CO₂ capture and release process is systematically investigated by means of ¹³ C NMR spectroscopy, differential scanning calorimetry (DSC), in situ FTIR analysis, and density functional theory (DFT) calculations, which could provide sufficient spectroscopic details to reveal the ease of reversibility and enable rational interpretation of the absorption mechanism.