Unexpected Crystallization Patterns of Zinc Boron Imidazolate Framework ZBIF‐1: NMR Crystallography of Integrated Metal–Organic Frameworks

Framework materials, that is, metal–organic frameworks (MOFs) and inorganic frameworks (zeolites), are porous systems with regular structures that provide valuable properties suitable for sorption, catalysis, molecular sieving, and so on. Herein, an efficient, experimental/computational strategy is presented that allows detailed characterization of a polycrystalline MOF system, namely, zinc boron imidazolate framework ZBIF‐1, with two integrated unit cells on the atomic‐resolution level. Although high‐resolution 1H, 11B, 13C, and 15N MAS NMR spectra provide valuable structural information on the coexistence of two distinct asymmetric units in the investigated system, an NMR crystallography approach combining X‐ray powder diffraction, solid‐state NMR spectroscopy, and DFT calculations allowed the exact structure of the secondary crystalline phase to be firmly defined and, furthermore, the mutual interconnectivity of the two crystalline frameworks to be resolved. Thus, this study shows the versatility and efficiency of solid‐state NMR crystallography for the investigation of the wide family of MOF materials with their extensive structural complexity. Second phase revealed: A secondary crystalline phase (ZIF) in zinc boron imidazolate framework ZBIF‐1 is revealed and defined by using the NMR crystallography approach. The interconnection between ZBIF‐1 and ZIFzni metal‐organic networks is assessed by solid‐state 1H–1H DUMBO/MAS NMR spectroscopy (see figure). Finally, the sizes of the observed domains are discussed.