To correlate defect sites with node distortions, we modeled 10 different {Zr 6 } clusters, including pure linker defects, pure O-vacancy defects from cluster dehydration, and combinations of both. Table and Scheme 1 summarize these defect types. Each cluster was geometry-optimized using DFT calculations, and PDFs were simulated and plotted in Scheme 1. The clusters differ in the number and type of charge-balancing OH/H 2 O species and the presence of one or two O-vacancies (see supplementary information for details). The first cluster in Table and Scheme 1, g 0 , with the composition [Zr 6 O 4 (OH) 4 (CH 3 COO) 12 ] represents the defect-free pristine DUT-67 structure. Organic ligands were replaced with formate ions to simplify the models, as tdc 2-and acetate ligands minimally affect PDF signals. The cartoons depict the octahedral {Zr 6 } cluster to have 4 Zr atoms and 4 ligands in a plane perpendicular to the view. For the linker defects, always 4 linkers in the same plane (perpendicular to the viewing axis) were considered. Below each model, the simulated PDF is shown together with the label, according to Table . Cluster-labeling g i,j is defined as i = 1; pure linker defects, without O-vacancies. i = 2; O-vacancies with 12 bridging formate ligands. i = 3; O-vacancies with four chelating formate ligands. i = 4; Ovacancies with four hydrolyzed formate ligands where two terminal aqua groups replace one formate group (charges were compensated through 4 OH -groups H-bonded to the cluster. The index j refers to the number of removed µ 3 -OH groups for g i=2,3,4 or for variations in the linker-defect type for g i=1 . and) shows the cases with combined linker defects and cluster dehydration. We note that for the linker defect type g 1,1 , 4 additional OH -for charge compensation are H-bonded to the cluster as described in Trickett et al. They are not shown in the cartoons and structural models but were included in the DFT calculations and PDF modeling. To identify the dominant distortions in aDUT-67, we conducted a two-phase fit of the PDF, using g 0 (non-defective cluster) as phase 1 and, subsequently, each defective cluster with O-vacancies (with and without linker defects) as phase 2. We included the pristine cluster in the analysis because the EXAFS fitting (Figure ) indicated that not Zr sites are converted to Zr cus sites. We did not consider pure linker defect clusters, as they do not produce significant peak splitting in the second shell. The fitted two-phase models,