A family of bulk and SBA-15 supported peroxo niobic acid sols were prepared by peptisation of niobic acid precipitates with H2O2 as heterogeneous catalysts for aqueous phase glucose and fructose conversion to 5-hydroxymethylfurfural (5-HMF). Niobic acid nanoparticles possess a high density of Brønsted and Lewis acid sites, conferring good activity towards glucose and fructose conversion, albeit with modest 5-HMF yields under mild reaction conditions (100 °C). Thermally-induced niobia crystallisation suppresses solid acidity and activity. Nanoparticulate niobic acid dispersed over SBA-15 exhibits pure Brønsted acidity and an enhanced Turnover Frequency for fructose dehydration.
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Funding: EPSRC (EP/K014706/1, EP/K000616/2, EP/K014676/1 and EP/K014749/1); and the Royal Society and British Council Global Innovation Initiative for GB3-Net.
Electronic supplementary information (ESI) available: Additional structural
and reactivity data. See DOI: 10.1039/c6cy01129b