Nanostructured Carbon-Doped BN for CO2 Capture Applications.

Carbon-doped boron nitride (denoted by BN/C) was prepared through the pyrolysis at 1100 °C of a nanostructured mixture of an alkyl amine borane adduct and ammonia borane. The alkyl amine borane adduct acts as a soft template to obtain nanospheres. This bottom-up approach for the synthesis of nanostructured BN/C is relatively simple and compelling. It allows the structure obtained during the emulsion process to be kept. The final BN/C materials are microporous, with interconnected pores in the nanometer range (0.8 nm), a large specific surface area of up to 767 m2·g-1 and a pore volume of 0.32 cm3·g-1. The gas sorption studied with CO2 demonstrated an appealing uptake of 3.43 mmol·g-1 at 0 °C, a high CO2/N2 selectivity (21) and 99% recyclability after up to five adsorption-desorption cycles.

Microporous Borocarbonitrides BxCyNz: Synthesis, Characterization, and Promises for CO2 Capture.

Porous borocarbonitrides (denoted BCN) were prepared through pyrolysis of the polymer stemmed from dehydrocoupled ethane 1,2-diamineborane (BH3NH2CH2CH2NH2BH3, EDAB) in the presence of F-127. These materials contain interconnected pores in the nanometer range with a high specific surface area up to 511 m2 · g-1. Gas adsorption of CO2 demonstrated an interesting uptake (3.23 mmol · g-1 at 0 °C), a high CO2/N2 selectivity as well as a significant recyclability after several adsorption-desorption cycles. For comparison's sake, a synthesized non-porous BCN as well as a commercial BN sample were studied to investigate the role of porosity and carbon doping factors in CO2 capture. The present work thus tends to demonstrate that the two-step synthesis of microporous BCN adsorbent materials from EDAB using a bottom-up approach (dehydrocoupling followed by pyrolysis at 1100 °C) is relatively simple and interesting.

Water Formation in Non-Hydrolytic Sol-Gel Routes: Selective Synthesis of Tetragonal and Monoclinic Mesoporous Zirconia as a Case Study.

Several non-hydrolytic sol-gel syntheses involving different precursors, oxygen donors, and conditions have been screened aiming to selectively produce mesoporous t-ZrO2 or m-ZrO2 with significant specific surface areas. The in situ water formation was systematically investigated by Karl Fisher titration of the syneresis liquids. XRD and nitrogen physisorption were employed to characterize the structure and texture of the ZrO2 samples. Significant amounts of water were found in several cases, notably in the reactions of Zr(OnPr)4 with ketones (acetone, 2-pentanone, acetophenone), and of ZrCl4 with alcohols (benzyl alcohol, ethanol) or acetone. Conversely, the reactions of Zr(OnPr)4 with acetic anhydride or benzyl alcohol at moderate temperature (200 °C) and of ZrCl4 with diisopropyl ether appear strictly non-hydrolytic. Although reaction time and reaction temperature were also important parameters, the presence of water played a crucial role on the structure of the final zirconia: t-ZrO2 is favored in strictly non-hydrolytic routes, while m-ZrO2 is favored in the presence of significant amounts of water. 1 H and 13 C NMR analysis of the syneresis liquids allowed us to identify the main reactions responsible for the formation of water and of the oxide network. The morphology of the most interesting ZrO2 samples was further investigated by electron microscopy (SEM, TEM).