The prediction and synthesis of new crystal structures enable the targeted preparation of materials with desired properties. Among porous solids, this has been achieved for metal–organic frameworks1, 2, 3, but not for the more widely applicable zeolites4, 5, where new materials are usually discovered using exploratory synthesis. Although millions of hypothetical zeolite structures have been proposed6, 7, not enough is known about their synthesis mechanism to allow any given structure to be prepared. Here we present an approach that combines structure solution with structure prediction, and inspires the targeted synthesis of new super-complex zeolites. We used electron diffraction to identify a family of related structures and to discover the structural ‘coding’ within them. This allowed us to determine the complex, and previously unknown, structure of zeolite ZSM-25 (ref. 8), which has the largest unit-cell volume of all known zeolites (91,554 cubic ångströms) and demonstrates selective CO2 adsorption. By extending our method, we were able to predict other members of a family of increasingly complex, but structurally related, zeolites and to synthesize two more-complex zeolites in the family, PST-20 and PST-25, with much larger cell volumes (166,988 and 275,178 cubic ångströms, respectively) and similar selective adsorption properties. Members of this family have the same symmetry, but an expanding unit cell, and are related by hitherto unrecognized structural principles; we call these family members embedded isoreticular zeolite structures.
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Extended data figures and tables
Extended Data Figures
- Extended Data Figure 1: Characterization of ZSM-25 and PST-20 zeolites. (83 KB)
a, b, PXRD patterns (left panels), 27Al (middle panels) and 29Si (right panels) magic-angle spinning NMR spectra of as-made (bottom plots within each panel) and calcined (top plots within each panel) ZSM-25 (a) and PST-20 (b).
- Extended Data Figure 2: Reconstructed 3D reciprocal lattice from the RED data. (65 KB)
a–c, NaTEA-ZSM-25 and d–f, NaSrTEA-PST-20. a, d, The 3D reciprocal lattice with the crystal inset. b, c, e, f, 2D slices cut from the reconstructed 3D reciprocal lattice showing the (hk0) plane (b, e), (hkh) (c) and (f) reciprocal plane. The distributions of the strong reflections for NaTEA-ZSM-25 and NaSrTEA-PST-20 are similar to that of PAU.
- Extended Data Figure 3: Structure factor amplitudes and phases calculated from the structure models of RHO-G1 to RHO-G6. (562 KB)
The reflections are shown. Reflections in red and blue have phases of 0° and 180°, respectively. The red, green and blue circles correspond to d-spacings of 1.0 Å, 1.6 Å and 3.0 Å, respectively. The frameworks are idealized in the pure SiO2 forms.
- Extended Data Figure 4: PXRD profiles for the Rietveld refinement of as-made and Na+-exchanged NaSrTEA-PST-20. (339 KB)
Top, as-made NaSrTEA-PST-20. Bottom, Na+-exchanged NaSrTEA-PST-20 (denoted NaTEA-PST-20). The observed, calculated and difference curves are shown in blue, red and black, respectively. The good agreement of observed and calculated data at high angles (inset) indicates that the framework structure is correct. The slight differences at lower angles are due to incomplete determination of the positions of all guest molecules/cations (X-ray wavelength λ = 0.40091 Å).
- Extended Data Figure 5: The prediction of the RHO-family members RHO-G1 to RHO-G6 from the structure of PAU (RHO-G3). (1,194 KB)
The arrows indicate how the structures were predicted from their nearest generations. The 3D electron-density map of RHO-Gn (n = 4–6) was generated using the structure factors of strong reflections from RHO-G(n − 1), which allowed a 3D structure model of RHO-Gn to be built. The structures of RHO-G1 and RHO-G2 were obtained from RHO-G3 by model building.
- Extended Data Figure 6: Tile representations of the structures of RHO-G1 to RHO-G6 in the RHO family. (280 KB)
The structure expansion operates at two levels: first, a pair of pau and d8r cages is inserted along each unit-cell edge (top) resulting in isoreticular expansion of the scaffold; and second, other cages are embedded (middle) in the inter-scaffold space. The resulting frameworks are denoted as ‘embedded isoreticular zeolite structures’ (bottom).
Extended Data Tables
- Supplementary Information (2.7 MB)
This file contains Supplementary Discussion (including the location of TEA+ cations in NaTEA-ZSM-25 by computational modelling), Supplementary Figures 1–9 and Supplementary Tables 1–17.