Powder neutron diffraction determination of the structure of the o-xylene/zeolite ZSM-5 complex

The structure of the complex of zeolite ZSM-5 (MFI) and ortho-xylene at a loading of four molecules per u.c. has been solved using powder neutron diffraction techniques and perdeuterated xylene. The structure is orthorhombic and the position and orientation of the organic is identical to that found previously by solid state NMR, attesting to the reliability of the NMR technique as a complement to diffraction methods. The maximum and minimum oxygen-oxygen distances of the elliptical 10-membered ring where the ortho-xylene is located are 8.86 angstrom and 7.45 angstrom, respectively, compared to corresponding distances of 9.13 angstrom and 7.32 angstrom found previously for the para-isomer, reflecting the different adjustments of the framework to the different sizes and shapes of the two guest molecules. (C) 2007 Elsevier Inc. All rights reserved.