“…(Keggin, 1933), [XM 12 O 40 ] nwith X a main group or a transition metal ion and M a transition metal ion, have been largely studied from a fundamental point of view (López et al, 2001;Maestre et al, 2001) and also because of of their applications in view of their interesting redox properties in relation to their micro-porosity in the salts of Keggin anions with various cations (Bonardet et al, 1995;Clemente-Léon et al, 1997;Katsoulis et al, 1998). (Keggin, 1933), [XM 12 O 40 ] nwith X a main group or a transition metal ion and M a transition metal ion, have been largely studied from a fundamental point of view (López et al, 2001;Maestre et al, 2001) and also because of of their applications in view of their interesting redox properties in relation to their micro-porosity in the salts of Keggin anions with various cations (Bonardet et al, 1995;Clemente-Léon et al, 1997;Katsoulis et al, 1998).…”