TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The mixture of gas comprises a combustion product. The acidic gas is an oxide of carbon, an oxide of sulfur, or an oxide of nitrogen, preferably carbon dioxide. The carbon-based fuel is coal, a petroleum product or natural gas.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The ionic liquid comprises pyrrolide having 0, 1, or 2 substituents, preferably 0 or 1 substituents. The ionic liquid comprises indolide having 0, 1, 2, or 3 substituents. The ionic liquid comprises an anion of formula ((Het.....CO2)-), or (a)-(d), preferably having heterocyclic structure of formula (a1)-(a5). The ionic liquid comprises at least one anion comprising fluoropyrrolide, 2-trifluoromethylpyrrolide, 1-fluoromethylpyrrolide, 2-cyanopyrrolide, difluoromethylpyrrolide, 1-fluoropyrrolide, 1-trifluoromethylpyrazolide, 1-cyanopyrrolide, methylesterpyrrolide, 1 -trifluoromethylpyrrolide, 1-acetylpyrrolide, and trichloroacetylpyrrolide.Dotted line = a covalent or non-covalent bonding interaction; andHet = optionally substituted heteroaryl;X = N or P;A = N or CR3;E = N or CR4;G = N or CR5;J = N or CR6; andR1-R10 = halo, CN, CNO, NCO, NO2, R11, OR11, SR11, NR12R13, -Y1-COZR11, SO2R11, SO3R11 or SO2NR12R13;Y1 = a single bond, optionally substituted 1-6C hydrocarbyl, -N(R12)-, O, or S;Z = a single bond, -N(R12)-, O, or S;R11 = H or optionally substituted 1-12C hydrocarbyl; andR12, R13 = H or optionally substituted 1-6C hydrocarbyl. EXAMPLE - Phosphonium bromide salt ((P66614)(Br)) was diluted with methanol (2M) and then transformed to ((P66614)(OH)) by adding 2:1 molar equivalents of an anion exchange resin (e.g. DOWEX SBR LC NG (OH) (RTM: Ion exchange resin)) in three batches, allowing 12 hours in between. The resin was pretreated with 1:1 volume equivalent of methanol by rinsing 3 times at room temperature since the resin was unstable at temperatures above 60 degrees C. During the ion exchange step, the mixture was stirred gently without a stir bar (which could deform the resin beads). After filtration to remove the resin, the (P66614)(OH) solution was mixed with a 1:1 molar equivalent of pyrrole-2-carbonitrile and stirred for 12 hours to obtain trihexyl(tetradecyl)phosphonium cyanopyrrolide ((P66614)(2-CNpyr)) and water. Excess methanol was removed by rotary evaporator at 50 degrees C and the (P66614)(2-CNpyr) solution was further dried under vacuum for 72 hours at 50 degrees C.