Structural changes of synthetic paulingite (Na,H-ECR-18) upon dehydration and CO2 adsorption

Alex G. Greenaway, Jiho Shin, Paul A. Cox, Elenica Shiko, Stephen P. Thompson, Stefano Brandani, Suk Bong Hong, Paul A. Wright

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The structure of dehydrated calcined ECR-18, synthetic paulingite, topology type PAU, unit cell composition Na132H28Si512Al160O1344, has been determined by Rietveld refinement against synchrotron X-ray powder diffraction data. Upon dehydration the symmetry of Na,H-ECR-18 changes from Im3m to I43m, with a corresponding decrease of cubic unit cell a parameter from 34.89412(1) Å to 33.3488(3) Å. This occurs as the framework distorts to afford closer coordination of Na+ cations by framework O atoms in 8-ring window sites of the seven cage types present. Na+ cations in 8R sites block the access of N2 molecules to the internal pore space at 77 K but CO2 adsorption at 308 K is observed, and is postulated to occur via a ‘trapdoor’ mechanism. In situ PXRD during CO2 adsorption at pressures up to 10 bar show reversible broadening of diffraction peaks that is attributed to local crystallographic strain.
Original languageEnglish
Pages (from-to)223-231
JournalZeitschrift für Kristallographie - Crystalline Materials
Issue number4
Early online date18 Mar 2015
Publication statusPublished - 1 Apr 2015


  • carbon dioxide adsorption
  • cation locations
  • dehydrated structure
  • synthetic paulingite
  • trapdoor zeolite


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