Absorbent for catching or separating dioxide carbon

The invention discloses an absorbent for catching or separating dioxide carbon, which is an aqueous solution of monoethanolamine and 1-butyl-3-methylimidazolium tetrafluoroborate. The concentration of the monoethanolamine in the absorbent is 100-300 g/L, and the mass ratio of the monoethanolamine to the 1-butyl-3-methylimidazolium tetrafluoroborate is 0.5-3. The absorbent has high-efficiency CO2 absorbency, such as high dioxide carbon absorption efficiency and absorption capacity, as well as high oxidation resistance, high temperature resistance and resistance to impact load, i.e., good stability; in addition, the absorbent is easy to regenerate and has the advantages of economy and easiness for industrialization.