PURPOSE: Non-aqueous carbon dioxide absorbent comprising sterically hindered secondary alkanolamine and diol is provided to reduce energy consumption required for regenerating the absorbent and to improve the absorption performance of carbon dioxide. CONSTITUTION: Non-aqueous carbon dioxide absorbent comprises secondary alkanolamine represented by chemical formula 1 and diol represented by chemical formula 2 or 3. In chemical formulas 1 to 3, R1 to R3 are respectively C1 to C4 alkyl groups; R4 to R6 are respectively hydrogen elements or C1 to C4 alkyl groups; R7 is a hydrogen element or a C1 to C4 alkyl group; m is the integer of 2 to 8; and n is the integer of 2 to 8. A method for separating carbon dioxide from a gas mixture includes the following: carbon dioxide is absorbed using the absorbent; and the absorbed carbon dioxide is degassed from the absorbent.
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