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<p>Zeolites are valued and extensively used industrially silicate materials with microporous framework structures containing uniform channels typically below 1&#xa0;nm in diameter. The efforts to synthesize new frameworks and crystal forms revealed another exceptional trait of zeolites, namely, that for the same topology, 2 forms are possible: the standard extended 3D crystals and 2D materials composed of nanosheets with uniform thickness below approximately 3&#xa0;nm. The latter can be converted to 3D frameworks by topotactic condensation, e.g., upon thermal treatment. They are named formally as layered zeolite precursors. So far, approximately 20 such precursors have been identified out of over 250 recognized 3D frameworks, but the number is gradually increasing (of both). Herein we analyze 2 recently reported structures designated ITQ-8 and PKU-22. ITQ-8 was described as related to zeolite levyne (LEV; zeolite structures are denoted with three letter codes) but its parent framework remained unrecognized. By analyzing structures in the online zeolite database, we identified SAS as the parent framework of ITQ-8, its formal precursor. The mentioned LEV topology is produced by joining the sas layers with additional single atoms, making it formally the so-called interlayer expanded zeolite form (IEZ). The layers of ITQ-8 and PKU-22 (parent structure stilbite, STI) are lacking in-plane mirror plane and produce different topologies by translation and mirror reflection operations. In addition to detailed presentation of the structures, we provide suggestions for experimental transformation of ITQ-8 and PKU-22 to the corresponding 3D frameworks.</p>

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Construction of known and hypothetical zeolites frameworks from layered precursors ITQ-8 and PKU-22 with SAS and stilbite layer topologies by different symmetry operations

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年7月8日

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  • Barbara Gil,
  • Wieslaw J. Roth

摘要

Zeolites are valued and extensively used industrially silicate materials with microporous framework structures containing uniform channels typically below 1 nm in diameter. The efforts to synthesize new frameworks and crystal forms revealed another exceptional trait of zeolites, namely, that for the same topology, 2 forms are possible: the standard extended 3D crystals and 2D materials composed of nanosheets with uniform thickness below approximately 3 nm. The latter can be converted to 3D frameworks by topotactic condensation, e.g., upon thermal treatment. They are named formally as layered zeolite precursors. So far, approximately 20 such precursors have been identified out of over 250 recognized 3D frameworks, but the number is gradually increasing (of both). Herein we analyze 2 recently reported structures designated ITQ-8 and PKU-22. ITQ-8 was described as related to zeolite levyne (LEV; zeolite structures are denoted with three letter codes) but its parent framework remained unrecognized. By analyzing structures in the online zeolite database, we identified SAS as the parent framework of ITQ-8, its formal precursor. The mentioned LEV topology is produced by joining the sas layers with additional single atoms, making it formally the so-called interlayer expanded zeolite form (IEZ). The layers of ITQ-8 and PKU-22 (parent structure stilbite, STI) are lacking in-plane mirror plane and produce different topologies by translation and mirror reflection operations. In addition to detailed presentation of the structures, we provide suggestions for experimental transformation of ITQ-8 and PKU-22 to the corresponding 3D frameworks.