In
recent decades, ionic liquids (ILs) have been developed as an
ideal and reversible decarbonization solvent. However, some pitfalls,
such as the low CO2 capacity and high viscosity of ILs,
limit their further scale up and industrial application. Therefore,
in this work, three novel functional ILs [N8881][NIA],
[N8881][For], and [N8881][Ac] were synthesized
after using a molecular design method to capture CO2 at
303.15–333.15 K and pressures up to 1000 kPa. The experimental
results illustrate that [N8881][NIA] presents the smallest
viscosity and the highest CO2 solubility. The capacity
order is [N8881][NIA] > [N8881][For] >
[N8881][Ac] under the same experimental conditions. The
CO2 recyclability experiments using [N8881][NIA]
show
the stability of CO2 solubility after 5 cycles. The quantum
chemistry simulations at the level of DFT/B3LYP with 6-311++G(d,p)
basis sets were used to study the CO2 absorption mechanism
in the studied ILs from the molecular viewpoint. Simulation results
illustrated that the higher interaction energy between CO2 and ILs means more CO2 absorbed in these ILs, which agreed
well with the experimental results. The atoms in molecules theory
and the function of the reduced density gradient were also used to
calculate the interactions in these IL–CO2 systems.
Results show that the majority of these interactions present an electrostatic
character.