ZrTFS was prepared with a "Shake 'n Bake" procedure that we have previously employed for the synthesis of several UiO-66 MOF analogues. In this procedure, a dense slurry of reagents in a small amount of a liquid is obtained instead of a clear solution upon a preliminary treatment using a ball mill. This probably induces a partial MOF crystallization before the heating stage, which provides a crystalline material at the end of the synthesis. If the milling stage is bypassed, a much less crystalline product is obtained (Figure ) and the reaction yield decreases from 88% to 69%. No solid product was obtained when larger volumes of water were used, suggesting that a high concentration of reagents is necessary to induce crystallization of ZrTFS. This is likely due to the high solubility of H2TFS in water, a result of its highly acidic character (pKa values of 1.64 and 3.68, determined using Chemicalize, , developed by ChemAxon). Notably, to the best of our knowledge ZrTFS is only the second material with an extended three-dimensional framework built with tetrafluorosuccinic acid reported in the Cambridge Structural Database, the other one being a lithium derivative. The structure of ZrTFS was solved ab initio from PXRD data using the parallel tempering algorithm implemented in the FOX program and refined with the Rietveld method using TOPAS. Details of structure solution and refinement are reported in the Supporting Information (Figure ). A polyhedral representation of the structure as obtained from the Rietveld refinement is reported in Figure . The structure was solved in the same cubic space group as MOF-801 (Pn-3) and it is fully consistent with the optimized DFT structure (see below).