This investigation demonstrated that bicarbonate ions were selectively formed over carbamate in a CO 2 absorption process using piperidine and piperazine derivatives based on 13 C NMR. Piperidines with methyl or hydroxymethyl substituent at 2 position (PiP-Me and PiP-MeOH) and 2, 5-dimethylpiperazine (DM-PiZ) generated the bicarbonate ions as main adducts in reaction with CO 2. The absorptions of CO 2 by those aqueous amines ( ...