The third category includes the pore volume measurements that exceed the geometric value, ≈11.7 % of the total. Possible hypotheses include an error in the structure-isotherm match or the crystal structure itself, a significant presence of defects in the crystal (e.g., missing ligands), or an unreliable measurement due to significant uptake on the surface of the crystal (e.g., small and packed crystals or jagged surfaces that create mesoporous interstices for probe molecules to adsorb outside the bulk of the crystal). MOFs with very strong bonds between nodes and ligands are known to display higher percentages of missing ligands: typical examples being UiO-66 and MOFs constructed from the Zr 6 O 8 secondary building unit. We emphasize that the possible explanations of the observed deviation listed above are hypotheses based on our experience and the inspection of individual cases in this work. In particular, this study has allowed us to identify materials for which characterization isotherms are reported by several independent studies and to compare them. The eight materials with the highest number of characterization isotherms (yellow markers in Figure ) are listed in Table . Histograms for the pore volume for each individual material are shown in Figure , and the full set of nitrogen isotherms are plotted in Figure . The examples of IRMOF-1 and CuBTC show a high spread of saturation uptakes (and therefore measured pore volumes), with an apparent multi-modal distribution. In this context, the geometrical pore volume from the crystal structure is an absolute reference that helps pinpoint which reports involve highly crystalline and fully activated materials -an insight that would be difficult to gain from relative statistical analysis alone (e.g., using the method of Sholl and co-workers). For CuBTC, the material with the most characterization isotherms (78 in total), we proceeded inspecting isotherm and paper, manually. No significant error related to the digitization process or the extraction of the pore volume from the isotherm was found (and the pore volume reported by the authors, when present, was similar to the one computed by us). We also note that while many of the reports contained CuBTC modifications or composite materials, the isotherms flagged as related to CuBTC in the NIST-ISODB indeed referred to the pristine version of the MOF, since it is often reported as a benchmark before further modification. However, this evidence suggest that algorithms that try to parse these values from the manuscripts via natural language processing may be particularly prone to errors, requiring elaborate tuning or the supervision by an expert reader. When the characterization isotherms indicated a weakly porous CuBTC (< 0.4 cm 3 g -1 ), this fact was usually mentioned by the authors (e.g., in the case of pellets, 55 or alternative synthesis routes ). Among the isotherms from which we computed a low pore volume in the range of 0.4 cm 3 g -1 to 0.5 cm 3 g -1 , some authors attribute the low porosity to partial activation. In many other cases, however, authors did not recognize the pore volume of their sample as low, despite it being less than half of the theoretical pore volume of the perfect, solvent-free crystal (as well as some of the highest reported experimental values).