Biomaterials for CO₂ harvesting: From regulatory functions to wet scrubbing applications

A new series of 2-aminoethyl-benzene-based biomaterials, namely, dopamine (DOP), tyramine (TYR), phenylethylamine (PEA), and epinephrine (EPN), dissolved in dimethylsulfoxide (DMSO) have been investigated for CO₂ capture upon activatiing their hydhydrochloride salts with a NaOH pellet. Spectroscopic measurements, including ex situ ATR-FTIR, 1D and 2D NMR experiments have been applied to verify the formation of the sodium carbamate adducts (RR′N-CO₂⁻ Na⁺). The emergence of new peaks in the IR spectra ranging between 1702 and 1735 cm⁻¹ together with the chemical shift within 157−158 ppm in the ¹³C NMR, as well as with cross-peaks obtained by ¹H-¹⁵N HSQC measurements at ca. 84 and 6.6 ppm verified the formation of RR′N-CO₂⁻ Na⁺ products upon the chemical fixation of CO₂. The CO₂ sorption capacity of the examined biomaterials was evaluated volumetrically, with a maximum value of 8.18 mmol CO₂·g⁻¹ sorbent (36.0 (w/w)%, including both chemisorption and physisorption), for 5 (w/v)% solutions measured at 5 bar CO₂ and 25 °C, for TYR and PEA. DFT calculations indicated that the intramolecular hydrogen bonding within the structural motif of EPN-N-CO₂⁻ Na⁺ adduct provides an exceptional stability compared to monoethanolamine and other structurally related model compounds.