The largest Se-4f cluster incorporated polyoxometalate with high Lewis acid-base catalytic activity.

A 4p-4f cluster incorporated polyoxometalate (POM), namely, H 18 {[(H 4 pic) 4 Eu 10 Se 13 O 28 (H 2 O) 12 ](α-GeW 9 O 34 ) 4 ·40H 2 O (1-Eu, H 4 pic = isonicotinic acid), has been first synthesized and characterized. 1-Eu features an interesting four-shell structure, representing the largest Se-4f cluster incorporated POM known to date. Besides, 1-Eu exhibits excellent Lewis acid-base catalytic activity and reusablity in catalyzing the gram-scale dehydration condensation reaction of hydrazines and 1,3-diketones to synthesize polysubstituted pyrazoles.