1. University of Antwerp (UIA), Department of Chemistry, Universiteitsplein 1, B-2610 Wilrijk, Belgium, Center for Modeling and Characterization of Nanoporous Materials, TRI/Princeton, P.O. Box 625, Princeton, New Jersey 08542, and University of Utrecht, Department of Inorganic Chemistry and Catalysis, Debye Institute, Sorbonnelaan 16, 3508 TB Utrecht, The Netherlands