Computational Insights into Biomimetic CO₂ Hydration Activities of (Poly)borate Ions

Abstract

Borate-based compounds have been observed to be CO 2 capture agents in natural and synthetic setups. Carbon capture in such systems has been proposed to take place via hydration of CO 2 resulting in bicarbonate ion formation. Several experimental studies have reported borate-based catalysts for CO 2 hydration reaction, and the mechanism of the reaction has been proposed to follow the enzymatic carbonic anhydrase action. In view of the absence of detailed physical insights into the mechanistic aspects of borate-catalyzed CO 2 hydration, computational investigations were carried out in this study under the density functional theory framework to explain the mechanism of the reaction over borate-based systems. Three borate-based systems, namely, borate ions, triborate ions, and tetraborate ions, were tested as the catalysts for the aqueous phase carbon capture reaction. Free energy landscapes provided the details of the elementary steps of the reaction, concluding the mechanism of the reaction to be indeed biomimetic consisting of parallel and bent CO 2 complexation, intramolecular proton transfer, bicarbonate ion complex formation and displacement of bicarbonate ion by water molecule to form (poly)borate−water complexes. All three ions were found to be active for catalyzing the reaction. NMR and FTIR spectra of all the intermediates proposed during the biomimetic mechanism were computed and compared against the experimentally reported spectra. The comparative analyses proved the identities of the intermediates, thus further confirming the mechanism of the reaction.

Mechanistic insights into biomimetic CO2 hydration activity of titania nanoclusters

“…NMR shielding (35.41 ppm) and NMR shift (157.20 ppm) of the HCO − 3 ⋯H 2 O complex differed from the HCO − 3 ion due to hydrogen bonding with the H 2 O molecule. 24 The above computational observations supported by experimental data validate the formation of OH − ⋅CO 2 and HCO − 3 ions over (TiO 2 ) 15 cluster, confirming the biomimetic CO 2 hydration mechanism shown in Figure 2.…”

“…With this concern, preparation of biomimetic analogues of carbonic anhydrase enzyme has become a new strategy for carbon capture in power plants and studies reporting synthetic analogues of carbonic anhydrases have found good attention in the scientific literature in the recent past. [18][19][20][21][22][23][24] Transition metal oxides have been prominent candidates for large-scale heterogeneous catalytic reactions, and, therefore, exploring the activities of transition metal oxides for CO 2 hydration following the carbonic anhydrase mechanism can be a good strategy for catalyst development. Recently, Mino et al 18 reported CO 2 , carbonate, and bicarbonate adsorption over TiO 2 surfaces.…”

“…The development of synthetic analogues is important because carbonic anhydrases have a limited use in large‐scale CO 2 capture due to their poor stability and short lifetime. With this concern, preparation of biomimetic analogues of carbonic anhydrase enzyme has become a new strategy for carbon capture in power plants and studies reporting synthetic analogues of carbonic anhydrases have found good attention in the scientific literature in the recent past 18–24 …”

Biomimetic Catalysis of CO2 Hydration: A Materials Perspective

“…This oxygen of the water molecule then attacks the carbon of CO 2 to from carbonic acid as seen in Figure 9c. Recently, Verma et al 153 reported computational insights into the biomimetic mechanism for bicarbonate ion formation in the presence of (poly)borate ions, and the Lindskog mechanism was found to be favored over the Lipscomb mechanism with lesser activation barrier. 3.3.…”

The Fructoborates: Part of a Family of Naturally Occurring Sugar–Borate Complexes—Biochemistry, Physiology, and Impact on Human Health: a Review

“…Recent research has shown that the development of HCO 3 − ion is stimulated by BCCs acting as CO 2 hydration catalysts. It appears that the mechanism involved is analogous to the enzymatic activity of carbonic anhydrase [ 86 ]. Practically, the buffer efficiency of the HCO 3 − (pH 7.4) is overtaken by the borate anion pairing with cis -diol esters through the appearance of some complexes with polyalcohols, sugars, and cis -diol organic acids (p K a 3.5–7.4) [ 4 ].…”