CATALYTIC-OXIDATION OF CYCLOHEXENE OVER T RANSITION-METAL SUBSTITUTEDPOLYOXOMETALATE PILLARED LAYERED DOUBLE HYDROXIDES

POM-LDHs with the composition of MAl-XW(11)ZO(39)(M=Zn, Mg; X=P, Si; Z = Mn2+, Fe2+, Co2+, Ni2+, Cu2+) were synthesized, and their catalytic properties for oxidation of cyclohexene in the presence of dioxygen w ere studied. The results obtained show that the oxidation of cyclohexe ne gives mainly alpha-H oxidation products, and the reaction activitie s greatly depend on the nature of the substituted transition metals in the POM pillars, i. e., with different Z ions, the activity is in the order: Co(2+)similar to Cu(2+)similar to Mn2+<<Ni(2+)similar to Fe2+, In addition the central atom in the POM pillars has some effects on t he oxidation of cyclohexene. The activity increases when P is used ins tead of Si, No obvious difference between the activities of ZnAl and M gAl layers were observed.