An Interrupted Zeolite PKU‐26 and Its Transformation to a Fully Four‐Connected Zeolite PKU‐27 upon Calcination.

Chen, Yanping; Ma, Ning; Huang, Shiliang; Du, Xin; Liao, Fuhui; Zhu, Yuexiang; Sun, Junliang; Wang, Yingxia

The thermal stability and structural transformation mechanism are critical for the industrial applications of zeolites and the design of new framework types. Herein, a new zeolite PKU‐26 has been hydrothermally synthesized under fluoride conditions using a tetraethylammonium (TEA ) cation as the structure‐directing agent (SDA) and its framework contains partial Q3 T atoms [Q3 for T(−O−T)3OH]. Upon calcination, PKU‐26 processed a single‐crystal to single‐crystal transformation to another novel zeolite PKU‐27 with the elimination of terminal −OH groups and enhanced thermal stability up to 650 °C, exhibiting the first Q3→Q4 transformation [Q4 for T(−O−T)4] in 3D zeolite frameworks. The mechanism of the structural transformation, involving proton transfer, framework dehydration, and TO4 reconstruction, is proposed and supported by theoretical calculations. Structural transformation from a new interrupted zeolite PKU‐26 to a thermal stable zeolite framework PKU‐27 upon heating demonstrates a novel Q3→Q4 transformation, in which the [4105462] CBUs in the pts layer of PKU‐26 change into the [32411526181] CBUs in the ptv layer of PKU‐27 by a mechanism involving proton transfer, framework dehydration, and TO4 reconstruction (see figure).

ZEOLITES; FLUORIDES; TETRAETHYLAMMONIUM; THERMAL stability; PROTON transfer reactions

Chemistry - A European Journal, 2019, Vol 25, Issue 13, p3219

0947-6539

Academic Journal

10.1002/chem.201805972