Economical Synthesis of Vanadia Aerogels via Epoxide-assisted Gelation of VOCl3
Herein is reported the first synthesis of vanadium oxide (vanadia) aerogels via epoxide-assisted gelation. Vanadia aerogels fabricated via epoxide-assisted gelation using VOCl3 and epichlorohydrin mimic those fabricated via the hydrolysis of vanadium oxytripropoxide while reducing cost per mole by a factor of 10, on par with silica gels synthesized from alkyl orthosilicates. Typical vanadia aerogels possess a macroporous nanoworm morphology, a density of 0.103 g/cm3, 96.9 % porosity, a specific surface area of 102 m2/g, and ~18 % reversible hydration capacity by mass. 1H and 13C NMR reveal that epoxide ring-opening does not proceed through epoxide protonation, as is the typical case with other transition metal oxide gels, but rather through Lewis-acid-catalyzed ring-opening. a multi-step gelation mechanism is proposed involving a fast initial VV oxide gelation, driven by H+ and Cl- consumption during epoxide ring-opening, followed by partial vanadia dissolution, VV → VIV reduction, and secondary gelation of low-valent VIV/V oxide.
T. M. Fears et al., "Economical Synthesis of Vanadia Aerogels via Epoxide-assisted Gelation of VOCl3," Journal of Sol-Gel Science and Technology, vol. 77, no. 1, pp. 244-256, Springer Verlag, Jan 2015.
The definitive version is available at http://dx.doi.org/10.1007/s10971-015-3850-x
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