The reaction of molybdates with multicarboxylic ligands resulted in the crystalline materials of [Na 8(Mo (VI) 10O 32EDTA)(H 2O) 35] n ( 1) and (NH 4) 8 n [Mo (VI) 10O 32PDTA] n (H 2O) 30 n ( 2) (EDTA = 1,2-diaminoethanetetraacetate; PDTA = 1,3-diaminopropanetetraacetate). In the two compounds, decamolybdate clusters are covalently linked by multicarboxylic ligands to form unusual meso-helical chains. For the first time, the synthesis of an organopolyoxometalate polymer is realized in aqueous media, which opens a green chemical approach to the fabrication of polyoxometalate-based polymers. The photochromic properties of 1 in the poly(vinyl alcohol) film displayed reddish-brown coloration upon UV irradiation, providing a new coloration material for photochromic films.