Ab initio analysis of the interaction of CO2 with acetylated d-glucopyranose derivatives

Peracetylated d-glucopyranose has a high solubility in CO2 and can be a promising phase-change physical solvent or absorbent for CO2, as reported recently. However, peracetylated d-glucopyranose is unstable under acidic atmospheres, especially in sulfur-containing waste gases, and the possibly major decomposition products are 2,3,4,6-tetra-O-acetyl-d-glucopyranose, 1-thiol-d-glucopyranose tetraacetate, and 1-mercaptoethyl-d-glucopyranose tetraacetate. Therefore, it is highly interesting to investigate the interaction between CO2 and these three compounds using ab initio calculations, including geometry optimizations with HF/3-21G, B3LYP/6-31+G** and single-point energy calibration with MP2/aug-cc-pVDZ. The results indicate that the electrostatic interactions between the substrates and CO2 are mainly influenced by the interaction distance and the numbers of negative charge donors or the interacting pairs involved in the complex. It is furthermore found that ΔE increases significantly if S and O atoms could interact with CO2 simultaneously. The binding energy is irrelevant if one considers the chemical environment of the O atom (i.e. OAc, OE or OS) or the S atom (i.e. SEt or SH), and the electronegativity difference between the S and O atoms. The three substrates studied are still excellent CO2-philes, although their average ΔE (–20 kJ/mol) is slightly lower than that of peracetylated d-glucose (–22 kJ/mol), which has one more O atom that can interact with CO2. Therefore, the applications of carbohydrates can be expanded to include adsorbents for CO2, SO2 or both, and the functional groups attached to the carbohydrate can vary from those to the acetyl groups.

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