The molecular characteristics dominating the solubility of gases in ionic liquids

The molecular characteristics dominating the solubility of gases in ionic liquids Yu-Feng Hu, * Zhi-Chang Liu, * Chun-Ming Xu, Xian-Ming Zhang State Key Laboratory of Heavy Oil Processing and High Pressure Fluid Phase Behavior & Property Research Laboratory, China University of Petroleum Beijing 09, China (E-mail: huyf358@sina.com; Fax: 86-0-8973386; Tel.: 86-0-8973386). Supporting information The solubilities of various gases in typical ionic liquids Table S Solubilities of various gases in typical ionic liquids ionic liquid(s) temperature(s) (K) pressure(s) a CO [C mim]([tf N], [TfO], [DCA]), [C mim][pf 6 ], [P 6,6,6, ][Cl] b 303.7 3.9 5 00 600 mmhg 5 [C 7 mim][tf N], [P n mim][tf N] ( n = 3) c 33.5 53 ~ atm 53 [C mim][meso ] 93. 3. 9 0.908 9.805 9 [C mim][pf 6 ], TMGL d 97.56 37.6 9 0.9 0.8 9 [C mim][pf 6 ] 33.5; 93 33.5 333.5; 95 98.5; 93.5 393.5; 9 33.5 333.5 93 3.0 5.0; 93 5; 95 and 5; 0.05 9.685; 9 0.0.93 93 [C mim][bf ], [C mim][pf 6 ] 303. 33. 9 0.96.39 9 ([C 6 mim], [P, ], [ETT])[FEP] e 83. 33.5 96 0.0077.800 96 [C mim]([tf N], [TfO], [DCA]), [P 6,6,6, ][Cl] 300.5 303.5 97,95 0.03 0.08 97,95 ([C mim], [C 3 --Memim], [C -3-MePy], 83.5 33.5 77 ~ bar 77

[perfluoro-hmim])[tf N], [C mim][bf ] f [C mim]([pf 6 ], [BF ]) 33.5 7 68 bar 7 ([C n mim], [C 8 H F 3 mim])[tf N] (n=3,, 6, 8), 98.5 00 bar 00 [C 3 mim][pf 6 ], [,-dibutyl-3-phenylimidazolium][tf N], [-butyl-3-phenylimidazolium][tf N] g [C 6 mim][tf N] 8.9 38.6; 0 93.5 3. 0 0.0089.976; 0 0.60 9.9 0 [C 6 mim][pf 6 ] 33.5 69 70 bar 69 [C n mim][tf N] ( n =, 6, 0 ) 98.5 33.5 89.35.708 89 [C mim][pf 6 ], [C mim]([tf N], [TfO], [DCA]), 303.5 95 < atm 95 [P 6,6,6, ][Cl] [P 6,6,6, ]([C H 5 PhSO 3 ], [MeSO 3 ]) h 307.55 3.5 99.8 8.96 99 [C mim]([tfa], [C 7 F 5 CO ]), ([C 8 H F 3 mim], 83.6 333.6 67 0 9.7 67 [C 6 H F 9 mim], [C 6-3-MePy], [b -Nic], [Choline], [N,,, ], [Et 3 NBH mim])[tf N], [N,,, ][DOC], Ecoeng 500, Ecoeng M, [C 5 mim][(c F 9 ) 3 PF 3 ], [C 6 mim]([(c F 5 ) 3 PF 3 ], [(C 3 F 7 ) 3 PF 3 ], [Tf N], [ACE], [SAC]) i [C mim]([bf ], [Tf N]), [C mim][pf 6 ], 98.5 03 0.6 0.97 03 [C 6 mim]([pf 6 ], [BF ], [Tf N]) [C mim][bf ], [C mim][dca] 98 35 05 ~ 05 [C mim][y], ([C n mim], [C 6 --Memim])[Tf N] ( n = 6, 8) j HEF, HEA, HEL, THEAA, THEAL, HEAF, 98. 333. 66 0.975 6.39 bar 66 303 33 07 0. 0.98 07 HEAA, HEAL k

[C mim][mdegso ] l 303. 33. 08 0.8 6.70 08 [C mim][tfo] 303. 33. 09 0.80 5.88 09 [C mim][bf ], [C mim]([bf ], [PF 6 ], [Tf N], 303.5, 33.5 86 0. 0. 86 [TfO], and [DCA]) [C mim][tf N] 303.63 3.3 30 3.30 57.0 kpa 30 ([C 8 mim], [C 0 mim], [C 8 H F 3 mim])[tf N] 98.0 33. 03 3.6 83.59 kpa 03 [C mim]([tf N], [B(CN) ]), [C mim]([dca], room temperature 09 0 atm 09 [C(CN) 3 ]) ([C -3-MePy], [C 8 mim], [C 6 mim])[bf ], 83.5 33.5 08 bar 08 [C 6 mim][tf N], [C mim]([tf N], [BETI], [TFA], [TfO]) m [C mim][ac] 83. 38. 00 0.00.999 00 [C mim]([tfsa], [NMes ]) n 93.5 0 atm 0 [hemim]([pf 6 ], [TfO], [Tf N]) o 303.5 353.5 56 0.097.8 56 CO, CF 3 CFH, SO, and NH 3 [C mim][tf N], [C mim]([pf 6 ] and [MeSO ]), 8.0 3. 87 0 0 87 [C 6 mim]([cl] and [Tf N]) [C mim][pf 6 ] CO [C mim][pf 6 ] H S [C mim][meso ] CO vapor liquid liquid equilibra 83. and 93.0 88. 5.8 88 73.6 3. 88.0 5. 88 75. and 9.5 0 3.6 6 0 CO absorption isotherms ([C mim], [C --Memim])[Tf N], 83.5 33.5 7 0 3 bar 7 ([C mim], [C --Memim])([PF 6 ], [BF ]) 3

([C mim], [C mim])([tfa], [Ac]), 97.3 98.3 86 0.009.000 86 ([C mim], [C 6 mim])[tf N], [C mim]([pf 6 ], [BF ], [PRO], [ISB], [TMA], [LEV], [TFES], [SUC], [IAAc]), [TBP][FOR], [C 6 mim][fap], [C mim] [IDA] p [C mim]([tfa], [Ac]) 98. 38. 87 0.000.9998 87 [C mim][tfo], [C mim]([etso ], [DCA]) 303. 33. 0 0.8 6.5 0 [Choline][Pro] q 33.5 ambient pressure [C 6 mim][tfo], [N,,,3 ][Tf N] 33. 33.39.3 9.66 bar [C n mim][bf ] ( n =, 6, 8) 307.55 3.5 3.75 9.00 3 P[VBTMA][BF ], P[VBMI][BF ] r 98.5 38.5 5 0 80 bar 5 [C n mim][(c n ) PO ] (n=,, ) s 33.5 333.5 7.3 98.8 kpa 7 [C mim]([pf 6 ], [BF ]) 8.75 38.5 90 0.00969.0000 90 phase behavior of the system(s) IL CO [C n mim][pf 6 ] (n=,, 6) 93 366 9 97 9 [C mim]([pf 6 ], [NO 3 ]), [C 8 mim]([pf 6 ], [BF ]), 33.5 333.5 69 0.97 95.80 bar 69 [C Py][BF ], [C mim][etso ] t ([C mim], [hpmim])[no 3 ] u 93.3 368. 0 0.368.83 0 [C 6 mim][br] 33.5, 333.5 30.90 8.9 bar [C 0 mim][tf N] 33.5 73.00.0 73 [C mim][pf 6 ] 93.9 363.5 9 0.59 73.50 9

bubble-point data for different CO mole fractions of CO in the system IL CO [C mim][bf ] 78.7 368. 3 0.587 67.6 3 [C n mim][tf N] ( n =, 5 ) 9.6 363.55 0.60 59.805 [C mim]([ac], [TFA]) 93.5 363.8 79 0.30 75.56 79 [C 6 mim][pf 6 ] 98.3 363.58 88 0.6 9.60 88 [C mim][pf 6 ] 308. 366.03 89.9 97.0 89 [C 6 mim][bf ] 93.8 368.6 90 0.5 86.60 90 [C mim][tf N] 33.50 9.; 98 97.5 3.5 8 0..099; 98 0.60 3.7 8 [C n mim][tf N] ( n =,, 6, 8 ) 9.75 3.55 99 3.0 99 [C mim][tf N] 3.0 50.9 0 0.66.0 0 [C n mim][tfo] ( n =,, 6, 8 ) 303.85 3.55 06 0.68 37.80 06 [C mim]([tf N], [DCA]) 9.65 363.6 6 0.69 73.60 6 [C 8 mim][bf ] 308.0 363.9 0.57 85.80 [C mim]([bf ], [SCN]), [C mim][mp], [(ETO) IM][Tf N] v 9.35 38.5 59 0.5 38.6 bar 59 [C mim][cl] 353.5 373.5 80.5 36.96 80 [C 6 mim][tf N] 78. 368. 8 0. 3.89 8 m--heaa() w 3.93 363.6 0 0.80 80.500 0 m--heaf() x 93. 363. 0 0.9 5.90 0 CO ([C n mim], [C --Memim], [C --Memim], 95 50 bar 50 [C m Py], [C --MePy], [C --MePy], [C -3-MePy], [C 8-3-MePy], [C --MePy], [C --MePy], [C 8 --MePy], [N,,,-OH ], 5

[N,,8,-OH ], [P, ])[Tf N] (n=,,, 6, 8; m=,, 6, 8), ([C mim], [C mim], [C mim], [C 6 mim], [C 8-3-MePy])[BF ], [C mim]([pf 6 ], [SbF 6 ], [CF 3 CO ]), [P, ][TFA], [C -3-MePy][DCA], and etc. y CO, CO, and H (molecular simulation results) [C mim][pf 6 ] 93. 393.5 0.5 9 CO, Ar, and H (molecular simulation results) [C 6 mim][tf N] 33 573 07 8 500 bar 07 H O and CO (atomistic Monte Carlo simulation results) [C 6 mim][tf N] CO 333 3 5.0 00.0 bar 5 [C 6 mim][tf N] H O 98 5 0.5 3.76 kpa 5 CO, C H 6, and H [C 6 mim][tf N] 83.3 33. 8 8.8 98.573 kpa 8 CO, H, N, O, and CO [MDEA][Cl] z 33.5 333.5 05. 8.6 05 CO, ethylene, propylene, -butene, and,3-butadiene [C mim]([tf N], [TfO], [BETI]), [C mim][pf 6 ], 303.5 9,97 atm 9,97 [P 6,6,6, ][Cl] ([N,,,3 ], [N 6,,,3 ], [N 0,,,3 ], [N,,, ], [N 6,,, ], 303.5 98 atm 98 [N 0,,, ], [N,8,8,8 ], [N 6,,, ])[Tf N] [P 6,6,6, ]([Cl], [DCA], [Tf N]), [P,,, ][DBS] 303.5 3 atm 3 [P,,, ][DEP] aa CO, CH, and N 6

[NC(CH ) n mim][tf N]( n =, 3, 5 ), 33.5 56 atm 56 [HCC-C mim][tf N], ([C mim], [C mim], [C 6 mim])[tf N] [C mim]([tf N], [BF ]), 33.5 3 ~ atm 3 [C mim][tf N] [C mim][bf ] CH and N [C mim]([tf N], [DCA], [TfO]), [C 6 mim][tf N] 33.5 33 ~ atm 33 CO and H ([N,,, ], [C mim], [C mim])[tf N] 8.93 33.79 3 36.06.007 kpa 3 CO, C H 6, CH, O, N, H, Ar, and CO [C mim][bf ] 78.0 3.7 6.588 98.53 kpa 6 [C mim][pf 6 ] 83.5 33.7 7 38.36 96.00 kpa 7 ethane, ethene, propane, propene, isobutane, butane, -butene,,3-butadiene, and CO [C mim]([dca], [Tf N], [TfO]), 33.5 35 ~ atm 35 [C mim]([pf 6 ], [BF ]) [C mim][pf 6 ] 93. 373. 36.6 9.6 36 ([C mim], [N 6,,, ])[Tf N] 93.5 38 ~ atm 38 H O O [C mim]([pf 6 ], [BF ], [Tf N]), room temperature 70 ~ atm 70 [C --Memim]([PF 6 ], [BF ], [Tf N]), [bm im][tf N] ab SO 7

[C 6-3-MePy][Tf N], [C 6 mim][tf N] 98.5 333.5 70 0.39 3.9 bar 70 [C mim]([pf 6 ], [BF ]), TMGL 33.5 367.5 39 ~ atm 39 ([C mim], [TMGH])[BF ], 93.5 3.5 0 bar 0 ([C mim], [TMGH])[Tf N] ac [C mim]([meso 3 ], [HSO ], [PF 6 ], [BF ], [Ac], 308.5 38.5 ~ atm [Cl]), [C n mim][meso ] ( n =,,, 6 ) [C mim]([pf 6 ], [Tf N]), 98.5.0 bar [C n mim][bf ] ( n =,, 6 ) [C mim][meso ] (from the reference 3 cited in 83.5 38.5 0 0 0.3 0 ref. 0) [C 6 mim][tf N] 8. 38. 0 0.007 0.3003 0 [C mim]([bf ], [TFSA]), 93.5 3.5 63 bar 63 [TMGH]([BF ], [TFSA]) H O, C 6 H 6, CO, N O, C H, C H 6, O, and Ar [C mim]([pf 6 ], [BF ], [Tf N]), ([N,,, ], 83.5 33.5 6 0 3.0 bar 6 [P, ])[Tf N], [P,,, ][TOS] ad [C mim]([pf 6 ], [BF ]) room temperature 3 5 00 atm 3 [C mim][pf 6 ] 33.05 373.5.08 9.00 [C 6 mim][tf N] 93. 3. 5.76 9.89 5 [X][Y] ae 93 and 98 6 atm 6 CH (bubble-point curves) [C mim][tf N] 300.3 9. 83.50 6.05 83 H [C 6 mim][tf N] 93.3 3.3 7.7 9.58 7 CF 8

CHF 3 [C mim][pf 6 ] 308.0 367.5 96.60 5.6 96 [C mim][pf 6 ] 303.0 363. 9 0.58.0 9 C H 6 [C 6 mim][tf N] 93.7 368.0 8 0.388 3.070 8 CO, N, CH, and H ([C mim], [C 6 mim])[tf N], [C mim][bf ], 98.5 33.5 9 ~ atm 9 [C mim][meso ] CO and O [C 6 mim][tf N] 93.5 3.0 50 0.7 9.785 50 CO and O [C mim][bf ] 303.7 3.5 37 0.0773 0.0875 37 CF, C F 6, and C 3 F 8 [P 6,6,6, ][Tf N] 303.9 33.70 5 ~ atm 5 CH and Xe [C mim][meso ] 93. 3. 5.9.95 5 [C 6 mim][tf N] 93.3 3.3 53 0.886 9.563 53 H S [C mim]([tf N], [BF ], [PF 6 ]) 303.5 33.5 5 60.8 0 kpa 5 [C 6 mim]([tf N], [BF ], [PF 6 ]) 303.5 33.5 55 0.097.0 55 [C mim]([cl], [Tf N], [BF ], [PF 6 ], [TfO]), 98.5 60. 60 ([C mim], [C --Memim], [C --Memim], [C --MePy], [bnpy], [mbpy], [N,,,-OH ], 9

[N,,,-OH ], [C Py])[Tf N] af Supplementary Material (ESI) for Chemical Society Reviews CPL-TBAB ILs ag 303. 363. 85 ~ atm 85 [C mim][meso ] 98. 8 0.008 0.7509 8 [hemim]([pf 6 ], [TfO], [Tf N]) 303.5 353.5 06 0.06.839 06 CO and H [C mim][meso ] 93.5 3.5 6.5 9.33 6 [C mim][pf 6 ] 93 373 6 0 5 bar 6 CO and C 3 H 8 [C 6 mim][tf N] 98.5 63 0.57 0.80 63 CO and C H 6 ([P, ], [C mim], [N,,3,-OH ])[Tf N] ah 303.63 3.8 6 38.88 57.6 kpa 6 H and CO [C mim][c 8 SO ], [C mim][etso ] 83.6 33. 65 0.0380 0.038 65 CO and C H [C 8 mim][bf ], [CN-C 3 mim]([dca], [Tf N]), 303 33 66 atm 66 [C mim]([n-c 6 H 3 OO], [n-c 8 H 35 OO], [Tf N], [BF ]), [CN-C 3 --Memim]([DCA], [Tf N]) ai CO and H S [C mim][etso ] 303.5 353.5 57 3.7 56.8 kpa 57 bubble-point data of N O in the IL gas system [C mim]([bf ], [SCN]), [C mim][mp], 9.35 373.55 58 6. 30.0 bar 58 ([(OH) IM], [(ETO) IM])[Tf N] aj 0

C H and C H [C mim]([mehpo 3 ],[Me PO ]), [C mim]([mehpo 3 ], [BuHPO 3 ], [Me PO ], [Ac], 33 8 7.38 66.78 kpa 8 [TFA], [MeSO ], [BF ], [Tf N]), [P, ]([BuHPO 3 ], [Ac], [Tf N]) ak NH 3 [C mim]([ac], [EtSO ], [SCN]), [N -OH,,,H ][Ac] al 8.5 37.8 67 0.36 5.007 67 [C mim]([pf 6 ], [BF ]), 8. 355.8 68 0.0.860 68 [C mim][tf N], [C 6 mim][cl] [C n mim][bf ] ( n =,, 6, 8 ) 93.5 333.5 0.07 0.83 CH 3 F, C H 5 F, and CHF CHF [C mim][pf 6 ] 83.06 38.8 7 0.0097.9995 7 CO, CH F, CHF 3, C F 5 H, CF 3 CH F, CF 3 CH 3, and CHF CH 3 [C mim]([pf 6 ], [BF ]) 8. 38.3 7 0.0096.000 7 CF 3 CH F [C mim]([pf 6 ], [HFPS], [TPES], [TTES]), 8.0 38.5 73 0.0098 0.3506 73 [C mim][bei], [P 6,6,6, ][TPES], [P,,, ][HFPS] am [C 6 mim]([tf N], [BF ], [PF 6 ]) 98.5 38.5 76 0. 3.30 bar 76 CH F [C mim]([pf 6 ], [BF ], [Ac], [SCN], [MeSO ], [TFES], [HFPS], [FS], [TPES], [TTES]), 83.5 38.5 7 0.009.006 7 [C 3 --Memim]([TMeM], [Tf N]), [C mim]([bei], [Tf N], [TFES]), [C 3-3-MePy][Tf N],

[C -3-MePy][Tf N], [C 7 mim][tfes], [C mim][tfes] an CFCl 3, CHCl 3, CDCl 3, CFCl CF Cl and CHCl CF 3 (VLLE data of the system IL gas) [C mim][pf 6 ] 8.7 333.9 75 ~ atm 75 CO, propane, propene, butane, and -butene [C mim][tf N] 79.98 30.00 78 0.00.7999 78 CO, C H, C H 6, CH, Ar, O, CO, H, and N [C mim][pf 6 ] 83.5 33.5 9 0 3 bar 9 a Unit: MPa unless otherwise noted. b [C n mim] + =-alkyl-3-methylimidazolium cation, [Tf N] = bis(trifluoromethylsulfonyl)imide anion, [TfO] =trifluoromethanesulfonate anion, [DCA] =dicyanamide anion, [ P n, n, n 3, n ] + =quaternary phosphonium cation. c [P n mim] + =-(Oligo(ethylene glycol) monomethyl ether)-3-methylimidazolium cation. d TMGL=,,3,3-tetramethylguanidium lactate e [P, ] + =N-butyl-N-methylpyrrolidinium cation, [ETT] + =S-ethyl-N,N,N,N -tetramethylthiouronium cation, [FEP] =tris(pentafluoroethyl)trifluorophosphate anion. f [C n --Memim] + =,-dimethyl-3-alkylimidazolium cation, [C n -3-MePy] + =-alkyl-3-methylpyridinium cation, [perfluoro-hmim] + =-(3,,5,6-perfluorohexyl)-3-methylimdazolium =-methyl-3-(3,3,,,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)imidazolium cation. cation. g [C 8 H F 3 mim] + h [C H 5 PhSO 3 ] = dodecylbenzenesulfonates anion. i [TFA] =trifluoroacetate anion, [C 7 F 5 CO ] = pentadecafluorooctanoate anion, [C 6 H F 9 mim] + =-methyl-3-(3,3,,,5,5,6,6,6-nonafluorohexyl) imidazolium cation, [b -Nic] + =-butyl-nicotinic acid butyl ester cation, [ N n, n, n 3, n ] + =quaternary ammonium cation, [Et 3 NBH mim] + =(-methylimidazole)(triethylamine)boronium cation, [DOC] =docusate anion, Ecoeng 500=PEG-5 cocomonium methylsulfate, Ecoeng M=-butyl-3-methylimidazolium -(-methoxyethoxy)ethylsulfate, [(C F 9 ) 3 PF 3 ] = tris(nonafluorobutyl)trifluorophosphate anion, [(C F 5 ) 3 PF 3 ] =tris(pentafluoroethyl)trifluorophosphate anion, [(C 3 F 7 ) 3 PF 3 ] =tris(heptafluoropropyl)trifluorophosphate anion, [ACE] =acesulfamate anion, [SAC] =saccharinate anion. j [Y]=[BF ], [PF 6 ], [TfO], [NO 3 ], [Tf N], [DCA], and [methide]([methide] =tris(trifluoromethylsulfonyl)methide anion). k HEF=-hydroxy ethylammonium

formate, HEA=-hydroxy ethylammonium acetate, HEL=-hydroxy ethylammonium lactate, THEAA=tri-(-hydroxy ethyl)-ammonium acetate, THEAL=tri-(-hydroxy ethyl)-ammonium lactate, HEAF=-(-hydroxy ethoxy)-ammonium formate, HEAA=-(-hydroxy ethoxy)-ammonium acetate, HEAL=-(-hydroxy ethoxy)-ammonium lactate. l [MDEGSO ] =-(-methoxyethoxy) ethylsulfate anion, m [BETI] =bis(pentafluoroethylsufonyl)imide anion. n [TFSA] = bis(trifluoromethanesulfonyl)amide anion, [NMes ] =bis(methanesulfonyl)amide anion. o [hemim] + =-(-hydroxyethyl)-3-methylimidazolium cation. p [PRO] =propionate anion, [ISB] =isobutyrate anion, [TMA] =trimethylacetate anion, [LEV] =levulinate anion, [TFES] =,,,-tetrafluoroethanesulfonate anion, [SUC] =succinamate anion, [IAAc] =iminoacetic acid acetate anion, [TBP][FOR]=tetrabutylphosphonium formate, [FAP] = tris(pentafluoroethyl)trifluorophosphate anion, [C mim] [IDA]=bis(-butyl-3-methylimidazolium) iminodiacetate. q [Choline][Pro]=(-hydroxyethyl)-trimethyl-ammonium(S)--pyrrolidine-carboxylic acid salt. r P[VBTMA][BF ]=poly(pvinylbenzyltrimethyl ammonium tetrafluoroborate), P[VBMI][BF ]=poly(-(p-vinylbenzyl)-3-methyl-imidazolium tetrafluoroborate). s [(C n ) PO ] =dialkylphosphate anion. t [C n Py] + =-alkylpyridinium cation. u [hpmim] + =-(3-hydroxypropyl)-3-methylimidazolium cation. v [SCN] =thiocyanate anion, [MP] =methylphosphonate anion, [(ETO) IM] + =,3-diethoxyimidazolium cation. w m--heaa=n-methyl--hydroxy ethylammonium acetate. x m--heaf=n-methyl--hydroxy ethylammonium formate. y [C n --MePy] + =-alkyl--methylpyridinium cation, [C n --MePy] + =-alkyl--methylpyridinium cation, [N,,,-OH ] + =,-dimethyl--butyl--(-hydroxyethyl) ammonium cation, [N,,8,-OH ] + =,-dimethyl--octyl--(-hydroxyethyl)ammonium cation. z [MDEA][Cl]=-(-hydroxyethyl(methyl)amino) ethanol chloride. aa [DBS] =dodecylbenzenesulfonate anion, [DEP] =diethylphosphate anion. ab [bm im] + =-butyl-,3,,5-tetramethylimidazolium cation. ac [TMGH] + =,,3,3-tetramethylguanidinium cation. ad [P,,, ][TOS]=tri-isobutyl-methyl phosphonium p-toluenesulfonate. ae [X][Y]=[C mim]([bf ], [PF 6 ], [Tf N], [SbF 6 ], [TFA] and [TfO]), [C --Memim][Tf N], ([C 6 mim], [C 8 mim])[bf ], ([C Py], [P, ])[Tf N], [P 6,6,6, ][(C F 5 ) 3 PF 3 ]. af [bnpy] + =-benzylpyridinium cation, [mbpy] + =-benzyl--methylpyrrolidinium cation, [N,,,-OH ] + =,-dimethyl--ethyl--(-hydroxyethyl)ammonium cation. ag ILs based on different mole 3

ratios of caprolactam and tetrabutyl ammonium bromide. ah [N,,3,-OH ] + =,-dimethyl--propyl--(-hydroxyethyl)ammonium cation. ai [CN-C 3 mim] + = -butyronitrile-3-methylimidazolium cation, [n-c 6 H 3 OO] =palmitate anion, [n-c 8 H 35 OO] =stearate anion, [CN-C 3 --Memim] + =-butyronitrile-,3-dimethylimidazolium cation. aj [(OH) IM] + =,3-dihydroxyimidazolium cation. ak [MeHPO 3 ] =methylphosphonate anion, [BuHPO 3 ] =butylphosphonate anion. al [N -OH,,,H ] + =-(-hydroxyethyl)-,-dimethylammonium cation. am [HFPS] =,,,3,3,3-hexafluoropropanesulfonate anion, [TPES] =,,-trifluoro--(perfluoroethoxy) ethanesulfonate anion, [TTES] =,,-trifluoro--(trifluoromethoxy)ethanesulfonate anion, [BEI] =bis(pentafluoroethylsulfonyl)imide anion. an [FS] = -(,,,-tetrafluoroethoxy)-,,,-tetrafluoroethanesulfonate anion, [TMeM] =tris(trifluoromethylsulfonyl)methide anion. Experimental Procedures Samples. CHCl 3 was supplied by Beijing Xiandaidongfang Chmical Ltd. [C 6 mim][(c F 5 ) 3 PF 3 ], [C mim][tf N], and [C 6 mim][tf N] were purchased from MercK with the claimed purity more than 99%. [P, ][Br] was prepared according to literature methods. 8,66 [P, ][Tf N], [C mim][dca], and [C mim][pf 6 ] were prepared with the well-established procedures of our and other previous works. 8,66 68 The ILs before use were dried under vacuum over CaCl for days at 353 K, and were further dried with 3 Å molecular sieve for days immediately. The water content after drying before use, measured by Karl Fisher titration, was less than 0.0 wt%. Raman spectra measurements. The Raman spectra were obtained using a HR800 micro-raman spectrometer (Jobin Yvon, France) employing a 785 nm laser beam, and the instrument resolution is 0.5 cm. 3 The temperatures ranging from 73 to 353 K on the sample were controlled using a Linkam TS600 hot stage with a temperature stability of ± 0.5 K. The temperature was held for at least 5 min at each selected temperature point in order to get more accurate temperature value of the sample. The Raman spectra were

measured in the crossed Z( XY ) Z ( VH ) and parallel Z( XY ) Z ( VV ) polarizations, where X, Y, and Z are the cubic axes. All these samples were sealed under vacuum in glass tubes for the Raman measurements. Analysis of the variation of G c with σ The G c is expressed as 3 G c 6y 8y πpσ 3 = ( r r) + r ln ( y) + r r + r RT y ( y) kbt 3 6 () σ+ σ σ It follows from r = that σ = σ r and r σ σ = + > () We then obtain σ 3 3 3 σ σ = = r 3 6 r r + r 3 6 (3) πpσ πpσ r r + r = kt 3 6 6kT B 3 3 3 B () and G c 6y 8 = ( r r) + r ln y + RT y ( y) 6k T 3 y πpσ ( ) B (5) If y is approximately regarded as a constant, then the effect of r on the G c is πpσσ = + + > 0 dr y ( y) kbt dgc 6y 36y RT ( r ) r (6) It is clear that, the r and thereby the G c is decreasing with increasing the σ. Comparisons of the solubilities of CO in [C mim][pf 6 ] and [C 6 mim][tf N] reported 5

in the literatures 9 8 7 Pressure, MPa 6 5 3 0 0.0 0. 0. 0.3 0. 0.5 CO, mole fraction Fig. S The CO solubilities in [C mim][pf 6 ] at 33 K: ( ) ([Cl] :.7 mg L ); 90 ( ) (H O: <00 ppm, [Br] : <50 ppm); 9 ( ) ([Cl] : 3 ppm). 9 8 7 6 Pressure, MPa 5 3 0 0.0 0. 0. 0.3 0. 0.5 0.6 0.7 0.8 CO, mole fraction Fig. S The CO solubilities in [C mim][pf 6 ] at 98 K: ( ) ([Cl] :.7 mg L ); 90 ( ) (H O: <00 ppm, [Br] : <50 ppm); 9 ( ) (H O: <00 ppm, halogen: <0 ppm); 03 ( ) (H O: 50 00 ppm, [Cl] : <0 ppm); 66 ( ) ([Cl] : 3 ppm). 9 6

6 5 Pressure, MPa 3 0 0.0 0. 0. 0.3 0. 0.5 0.6 0.7 0.8 CO, mole fraction Fig. S3 Comparison of the CO solubilities in [C 6 mim][tf N] in the 97 98 K range: ( ); 03 ( ); 67 ( ); 0 ( ); 0 ( ); 66 ( ) fitted values calculated using eqn (0). Comparisons of measured and fitted solubilities of CO in [C n mim][bf ] ( n =, 6 ), [C n mim][tf N] ( n =, 8), and [C 6 mim][pf 6 ] at different temperatures and pressures Pressure, MPa 9 8 7 6 5 3 0.5 0.0 0.5 0.30 0.35 0.0 0.5 0.50 CO, mole fraction Fig. S Comparisons of measured 3 (symbols) and fitted (lines) solubilities of CO in [C mim][bf ]:( ) 307.55 K; ( ) 3.5 K; ( ) 37.5; ( ) 3.5 K. 7

9 8 7 Pressure, MPa 6 5 3 0.0 0.5 0.30 0.35 0.0 0.5 0.50 0.55 CO, mole fraction Fig. S5 Comparisons of measured 3 (symbols) and fitted (lines) solubilities of CO in [C 6 mim][bf ]: ( ) 3.5 K; ( ) 37.5 K; ( ) 3.5 K. Pressure, MPa 9 8 7 6 5 3 0 0. 0.3 0. 0.5 0.6 0.7 0.8 CO, mole fraction Fig. S6 Comparisons of measured 66 (symbols) and fitted (lines) solubilities of CO in [C mim][tf N]: ( ) 98. K; ( ) 33.3 K; ( ) 333.3 K. 8

9 8 7 Pressure, MPa 6 5 3 0 0. 0.3 0. 0.5 0.6 0.7 0.8 CO, mole fraction Fig. S7 Comparisons of measured 66 (symbols) and fitted (lines) solubilities of CO in [C 8 mim][tf N]: ( ) 98. K; ( ) 33.3 K; ( ) 333.3 K. 8 7 6 Pressure, MPa 5 3 0 0.05 0.0 0.5 0.0 0.5 0.30 0.35 0.0 0.5 CO, mole fraction Fig. S8 Comparisons of measured 88 (symbols) and fitted (lines) solubilities of CO in [C 6 mim][pf 6 ]: ( ) 33.5 K; ( ) 33.5 K; ( ) 333.5; ( ) 33.5 K. 9

References 66. A. K. Burrell, R. E. Del Sesto, S. N. Baker, T. M. McCleskey and G. A. Baker, Green Chem., 007, 9, 9 5. 67. D. R. MacFarlane, J. Golding, S. Forsyth, M. Forsyth and G. B. Deacon, Chem. Commun., 00, 30 3. 68. J. Dupont, C. S. Consorti, P. A. Z. Suarez and R. F. de Souza, Org. Synth., 00, 79, 36. 0