Evaluation of Bronsted acidity and proton topology in Zr- and Hf-based metal-organic frameworks using potentiometric acid-base titration

Potentiometric acid-base titration is introduced as a method to evaluate pKa values (Bronsted acidity) of protons present in the nodes of water stable Zr-6- and Hf-6-based metal-organic frameworks (MOFs), including UiO-type MOFs, NU-1000, and MOF-808. pKa values were determined for the three typical types of protons present in these MOFs: mu(3)-OH, M-OH2, and M-OH (M = Zr, Hf). Additionally, the data was used to quantify defect sites resulting from either a surfeit or shortage of linkers in the MOFs and to provide information about the true proton topology of each material.