The reaction of molybdates with multicarboxylic ligands resulted in the crystalline materials of [Na-8(Mo-10(VI)-O(32)EDTA)(H2O)(35)](n) (1) and (NH4)(8n)[MO(10)(VI)O(32)PDTA](n)(H2O)(30n) (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 pholochromic films.