The outstanding diversity of Zr-based frameworks is inherently linked to the variable coordination geometry of Zr-oxo clusters and the conformational flexibility of the linker, both of which allow for different framework topologies based on the same linker–cluster combination. In addition, intrinsic structural disorder provides a largely unexplored handle to further expand the accessibility of novel metal–organic frameworks (MOFs) structures that can be formed. In this work we report the concomitant synthesis of three topologically different MOFs based on the same M6O4(OH)4 clusters (M = Zr or Hf) and methane-tetrakis(p-biphenyl-carboxylate) (MTBC) linkers. Two novel structural models are presented based on single crystal diffraction analysis, namely cubic c (4,12)MTBC-M6 and trigonal tr (4,12)MTBC-M6, which comprise 12-coordinated clusters and 4 coordinated tetrahedral linkers. Notably, the cubic phase features a new architecture based on orientational cluster disorder, which is essential for its formation and has been analyzed by a combination of average structure refinements and diffuse scattering analysis from both powder and single crystal X-ray diffraction data. The trigonal phase also features structure disorder, although involving both linkers and secondary building units. In both phases, remarkable geometrical distortion of the MTBC linkers illustrates how linker flexibility is also essential for their formation and expands the range of achievable topologies in Zr-based MOFs and its analogues.
Supplementary Information file
This file contains the supplementary information for this study. This includes additional details on synthetic procedures, characterization via powder and single crystal total scattering, microscopy, and topological analysis. All crystal structures described in our work can be obtained free of charge from the Cambridge Crystallographic Database at the web-page https://www.ccdc.cam.ac.uk/structures/. Their reference numbers are 2182237 (c-(4,12)MTBC-Zr6 with cubic morphology), 2215758 (c-(4,12)MTBC-Zr6 with tro morphology), 2206543 (c-(4,12)MTBC-Hf6 with tro morphology), 2206443 (tr-(4,12)MTBC-Zr6), and 2206530 (tr-(4,12)MTBC-Hf6).
3D electron density maps
This .zip folder contains the observed 3D electron density maps used for the modelling of the reported crystal structures, provided as “.vesta” and “.pgrid” files that can be opened via the free software Vesta. Additional information on their creation and usage can be found in the Supplementary Information file (Section S6.3).