Amine-functionalized cellulose polymers for CO2 capture

A method of preparing an amine-functionalized polymer comprises:

• contacting a cellulose polymer comprising a repeating unit of Formula 2:
• with an oxidant comprising (i) 0.1-10% wt laccase and 0.1-10% wt (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), wherein the cellulose polymer is present at a concentration of 0.5-2.0% wt, or (ii) 0.1-1% wt NaBr, 0.01-0.1% wt TEMPO, and 0.1-10% wt NaClO, wherein the cellulose polymer is present at a concentration of 5-10% wt, thereby forming an oxidized cellulose polymer comprising a repeating moiety of Formula 3:
• or a conjugate salt thereof, wherein
• R3 is —CO2H or —CHO;
• contacting the oxidized cellulose polymer with a polyalkylenimine or an alkylsilane, with the proviso that when R3 is —CO2H, a coupling agent is also present during the step of contacting the oxidized cellulose polymer with the polyalkylenimine or the alkylsilane;
• and thereby forming an amine-functionalized polymer comprising a repeating unit of Formula 1:
• or a conjugate salt thereof, wherein R1 is —(C═O)NHR2 or —H(C═N—R2);
• and R2 is a polyalkylenimine or an alkylsilane.