Pentaerythritol-Based Molecular Sorbent for CO₂ Capturing: A Highly Efficient Wet Scrubbing Agent Showing Proton Shuttling Phenomenon

Abstract

Pentaerythritol (PE) is considered a biodegradable material that combines the ease of synthesis, nonvolatility, and extra stability under basic conditions (acidic gas sequestration, e.g., CO 2 ), which makes it a useful candidate for postcombustion capture (PCC) application. To overcome corrosion problems associated with CO 2 binding organic liquids, a binary mixture comprised of PE/1,8-diazabicyclo-[5,4,0]-undec-7-ene (DBU) (1:4 molar ratio) dissolved in dimethyl sulfoxide (DMSO) was exploited for CO 2 capturing. The formation of ionic alkyl organic carbonate (RCO 3 – DBUH + ) was confirmed using 13 C NMR (157.4 ppm) and ex situ attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) (two peaks were identified, viz., 1670 and 1630 cm –1, which were ascribed to the symmetric and asymmetric stretching of both C═O and O ··· C ··· O − within RCO 3 H and RCO 3 –, respectively). The charged adduct was measured using a thermostated beaker coupled with conductivity and pH meter probes. The sorption capacity of a 5.0% PE (w/v) solution was measured volumetrically with high efficiencies as, ca. 16 and 18.5 wt %, for wet and dry conditions, respectively. In addition, density functional theory (DFT) was performed to understand the mechanism of action in the case of H 2 O, and simple alcohols, e.g., methanol and ethanol. Moreover, we reported on the newly discovered medium-dependent proton shuttling phenomenon that was verified experimentally and theoretically.