Potentiometric acid-base titration was introduced to measure pKa values (Brønsted acidity) of protons in Zr_6-based metal-organic frameworks (MOFs), including UiO-type MOFs and MOF-808. The pKa values of three typical types of proton present in these MOFs, μ_3-OH, Zr - OH_2, and Zr – OH were evaluated. The two latter protons are assumed to mainly originate from missing linker. From structural characterization using techniques such as TGA, NMR, and EDS, it seemed to not entirely be the case, since standard UiO-66-BDC was observed to not have any defects from the linkers, and the small amount of chloride detected may originate from the pores of the material rather than being part of the structure. Also, one of the two standard UiO-67s (UiO-67-400) which was amorphous, could seemingly detect protons similar to the other crystalline UiO-67-PM MOF and literature. This weakens the hypothesis that potentiometric acid-base titration is a good method to characterize MOFs. All materials were characterized by PXRD, SEM/EDS, TGA, and N2-adsorption. Additionally, the acidic properties of the titrated samples were compared with MP-AES, EDS, and TPD for zeolites and FT-IR for MOFs. FT-IR was applied to discover the same Brønsted acids that were detected by potentiometric acid-base titration. The μ_3-OH proton could be found with both techniques, but the others could not be detected by the preliminary FT-IR measurements that were carried out. Potentiometric acid-base titration was also used to find the available acid site density for commercial zeolites, involving H-USY (FAU), H-BEA-25 (*BEA), and H – β (*BEA), and H-ZSM-5 (MFI). MP-AES and EDS revealed a higher Si/Al ratio (lower Al content) in all the zeolites compared with the value that was provided by the suppliers. This would predict that fewer amount of acid sites would be detected when using potentiometric titration and TPD, which appeared to be the case. The results indicated good agreement between potentiometric acid-base titration and TPD since the measured density acid sites (μmol/g) showed values comparable to each other. This was especially the case for zeolites with low Al content.