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Evolution of a Metal-Organic Framework into Brønsted Acid Catalyst for Glycerol Dehydration to Acrolein.

Metal-organic frameworks (MOFs) as solid acid catalysts provide active sites with definite structures. Here, we studied Zr6-based MOF-808 and its derivatives as the catalysts for glycerol dehydration, whose product (acrolein vs. acetol) is very sensitive to the nature of the catalytic acid sites. Evolving MOF-808 into MOF-808-S with a 120% increase in the number of Brønsted OH-/H2O coordinated to Zr(IV) and vanished Lewis acidity by steam treatment, the post-synthetically modified catalyst presents 100% conversion of glycerol, 91% selectivity of acrolein, and 0% selectivity of acetol within the active window. Real-time analysis of the product composition indicates the in-situ MOF structural evolution. Overall, the specific MOF-substrate interaction characterized by the probe reaction provides more understandings on the structural evolution of the MOFs and their impact on the performance as solid acid catalysts.