Computational study of Bronsted acidity in the metal-organic framework UiO-66

UiO-66 is one of the most popular metal-organic framework materials for catalysis. The Bronsted acidity of its Zr-6-node is often critical to its catalytic power, but the acidity of each individual proton is difficult to measure directly in experiments. Here, we used density functional theory calculations to quantify the Bronsted acidity of different protons on both pristine and defective Zr-6-nodes. The calculated acidities were in a different order than the previously reported results that were indirectly assigned from titration. Additional computational analyses were performed to help explain the results and reveal the underlying factors that could affect the acidity.