Solubility data of carbon dioxide (CO

2

) (1) in methanol (2)

1-octyl-3-methylimidazolium bis(trifluoro- methylsulfonyl)imide ([omim

]

+

[Tf

2

N

]

-

) (3)

and their mixtures (w

3

0.2

0.5

and 0.8) at temperatures 313.2 and 333.2 K and pressures up to 7.0 MPa were measured by a high-pressure view-cell technique. The solubility of CO

2

in methanol (w

3

=0)

[omim

]

+

[Tf

2

N

]

-

(w

3

=1.0) and their mixtures follows the order of (w

3

=0)w

3

=0.2) (w

3

=0.5)w

3

=0.8)w

3

=1.0) at the same temperature and pressure

while the magnitude of Henry's constants follows the reverse order at a given temperature

which is consistent with the COSMO-RS (conductor-like screening for real solvents) calculation. The solubility data of CO

2

in methanol and [omim

]

+

[Tf

2

N

]

-

are correlated with the Peng-Robinson equation of state

and the solubility of CO

2

in the mixtures of methanol and [omim

]

+

[Tf

2

N

]

-

can be well predicted based on the mole fraction average of methanol and [omim

]

+

[Tf

2

N

]

-

over the solubility of CO

2

in pure methanol and [omim

]

+

[Tf

2

N

]

-

. The mixtures of methanol and [omim

]

+

[Tf2N

]

-

may be used as physical solvents for capturing CO

2

with high partial pressures since they combine the advantages of organic solvents and ionic liquids.