Biomimetic CO2 hydration activity of boronic acids.

Inspired by the recent experimental reports on boron containing compounds to be active and biomimetic for carbon capture, we report the mechanistic details of CO2 hydration activities of boronic acids using density functional theory calculations. Four boronic acids were analyzed, viz., [3-methyl-6-(1H-pyrazol-1-yl)phenyl]boronic acid, 3-aminophenylboronic acid, 2,6-dibromophenylboronic acid and 2,6-bis(trifluoromethyl)phenylboronic acid. Free energy landscapes were developed for the hydration reaction. 2,6-Dibromophenylboronic acid showed the highest turnover frequency. Computational NMR and FTIR spectra for various intermediates of the reaction were analyzed and compared with experimental spectra. The energetics as well as the spectral analyses confirmed the biomimetic mechanism for CO2 hydration over all the boronic acid catalysts under investigation.

On the stability of hydroxyl groups on substituted titania.

The present study reports the stability of hydroxyl groups involving the surface coordinated oxygens of Pd,C,N-doped, and Pd/C and Pd/N-codoped anatase TiO2, probed using DFT calculations. Two unique surface planes, (001) and (100), were chosen for the analysis of the stability of hydroxyl groups and their activities were studied by net oxygen activation analysis. The hydroxyl group formation energies ranged between -6.16 and -7.88 eV for the C,N-doped, and Pd/C and Pd/N-codoped TiO2(001) and (100) planes. The order of hydroxyl stability was observed to be TiO2(001) > TiO2(100) > Pd/C-codoped (001) > Pd/N-codoped (100) > Pd/C-codoped (100) > N-doped (001) > C-doped (100) > N-doped (100) > Pd/N-codoped (001) > C-doped (001) planes of TiO2. Although the formation energies of Pd/C and Pd/N-codoped TiO2 were marginally higher compared to those of the pure TiO2(001) and (100) planes, they exhibited a higher net oxygen activation of 32.1% and 28.9% over the surface exposed (100) plane, which indicated the better feasibility of reversible exchange of lattice oxygen. Electron density maps displayed the surface reconstruction phenomenon corresponding to the rearrangement of surface atoms and the transfer of electrons between O-H over the (001) and (100) planes of C,N-doped, and Pd/C and Pd/N-codoped TiO2.

On interaction of arginine, cysteine and guanine with a nano-TiO2 cluster.

Nanoscopic properties of TiO2 augmented with its physicochemical properties and biocompatibility make it a material interest in the biomedical field. Efficient methods to design of such materials require a thorough understanding of associated nano-bio interfaces. In the present study, density functional theory calculations were performed to study the interactions of arginine, cysteine and guanine with a nano-TiO2 cluster. Different configurations were sampled for the adsorption of arginine, cysteine and guanine to probe the nano-bio interface via the interaction of various functional groups present on biomolecules. Adsorption energies for arginine, cysteine and guanine were in a range of -25.0 to -57.6, -12.1 to -29.6 and -45.6 to -58.7 kcal/mol, respectively. From the change in adsorption energies and free energies, interaction of amino acids with carboxylic (COOH), thiol (SH) and amine (NH2) groups while the interaction of the nucleobase via O bonded to C and N of purine ring was found to be essential for thermodynamically stable and energetically favorable states. Density of states analysis also disclosed the prominent interactions of the biomolecules with the nano-TiO2 cluster. Decrease in band gaps on adsorption of the biomolecules was a pertinent phenomenon indicating the strong chemical interactions of the biomolecules with the nanoscopic TiO2 chosen for analysis in this study.