Enhanced catalytic performance of UiO-66 via a sulfuric acid post-synthetic modification strategy with partial etching

A post-synthetic modification strategy is performed on Zr-based metal-organic framework UiO-66 (UiO = University of Oslo) by treating with dilute sulfuric acid. After the modification by appropriate dosage of H₂SO₄, the original regular octahedral morphology, recrystallization and thermostability can be maintained while the surface is partially etched. It is found that S species are introduced chemically in the form of SO₄²⁻ by replacing monocarboxylic modulator ligands. However, the content of Zr is partially lost during the modification. By means of sulfuric acid modification, the strength and amount of acid sites are enhanced, which are crucial on the catalytic performance. The catalytic activity of the modified catalysts exhibits five times higher performance than the pristine UiO-66 in the acetalization of benzaldehyde and methanol, and the high catalytic efficiency can be retained after five runs.