Syntheses and structure of three 2D polyoxometalates derived from macrocation [Cr3O(COOH)6(H2O)3]+ and α-Keggin-type polyoxomolybdate anions

► Three novel organic-inorganic hybrid compounds with 2D infinitely extended structure were synthesized. ► Constructed from saturated Keggin-type polyoxomolybdates and trinuclear chromium formate macrocations. ► Polyoxomolybdate anions and macrocations are polymerized through the bridging K+ cations to form a 2D infinitely extended layer structure.