Ab initio gas phase calculations were performed to calculate the charges on each atom of the solvents and their interaction with CO2. For each molecule, the geometry optimization was performed by using B3LYP/6-311++g(d,p) followed by charge calculations by using the CHELPG protocol. The CO2-molecule dimer was also optimized by using B3LYP/6-311++g(d,p) followed by a single point energy calculation at the MP2/cc-pVTZ level of theory to obtain CO2 interaction with each molecule. To account for the basis set superposition error, we have used counterpoise corrections in both geometry optimization, frequency, and single point calculations for dimer computations. More calculation details were described in our previous work. All ab initio calculations were performed by using the Gaussian 09 program. All fractional free volume calculations were calculated by using a modified Bondi method, which has been implemented in an in-house software package at NETL. We have reported further details on this method in our previous work. Results and Discussion