Economical synthesis of vanadia aerogels via epoxide-assisted gelation of VOCl 3

Herein is reported the first synthesis of vanadium oxide (vanadia) aerogels via epoxide-assisted gelation. Vanadia aerogels fabricated via epoxide-assisted gelation using VOCl 3 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/cm 3 , 96.9 % porosity, a specific surface area of 102 m 2 /g, and ~18 % reversible hydration capacity by mass. 1 H and 13 C 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 V V oxide gelation, driven by H + and Cl − consumption during epoxide ring-opening, followed by partial vanadia dissolution, V V → V IV reduction, and secondary gelation of low-valent V IV/V oxide. Graphical Abstract