Microwave regeneration of carbon dioxide sorbents

A method for regenerating an amine-containing sorbent useful in CO2 capture, the method comprising exposing an amine-containing sorbent-CO2 complex in the solid state to microwave radiation having a frequency of 2-5 GHz and power output of at least 1500 W for about 30 seconds to result in release of CO2 and regenerated amine-containing sorbent that is uncomplexed with CO2, wherein the amine-containing sorbent-CO2 complex contains either:

• (i) a carbamate bond;
• or
• (ii) an ion pair bond of the formula
• wherein Ra, Rb, and Rc are selected from H and hydrocarbon groups containing at least one carbon atom, wherein at least one of Ra, Rb, and Rc is H;
• the dashed double bond represents the presence or absence of a double bond, and the dashed single bond represents the presence or absence of Rc, wherein Rc is present only if the double bond is not present;
• Xm− is a carbonate or bicarbonate anion, with m being 1 for bicarbonate and 2 for carbonate;
• and n is an integer of 1 or 2, provided that n×m=2;
• wherein the carbamate bond or ion pair bond results from direct or indirect reaction of at least one free amine group in the uncomplexed sorbent with CO2;
• wherein the amine-containing sorbent-CO2 complex is a solid complex;
• wherein the regenerated amine-containing sorbent contains at least one free amine group capable of directly or indirectly reacting with CO2 to produce the amine-containing sorbent-CO2 complex;
• and wherein the amine-containing sorbent is a bis(iminoguanidinium) compound having the following structure:
• wherein R1 and R2 are independently selected from H and methyl groups.