A new Keggin-type polyoxometalate-based supramolecular complex 1, namely H3 [ (3-PA)4 ( PW12O40) ] (3-PA = 3-Pyridineacrylic acid), was successfully synthesized under hydrothermal conditions and structurally characterized by single crystal X-ray diffraction, elemental analysis ( EA), IR spectra, PXRD, TG and UV-Vis diffuse-reflectance. Complex 1 crystallizes in the triclinic system, P-1 space group with α = 1. 200 33(3) nm, b = 1.216 42(3) nm, c = 1. 424 66(4) nm, α =75.030(1)°, β =73.452(1)°, γ =69.372(1)°, V = 1.837 00(8) nm³, Z = 1, Mr =3 476.78, F(000) = 1 538, µ = 18. 815 mm-1, Dc = 3. 143 mg⋅m-3, S = 1. 062, R1 = 0. 046 2, wR2 = 0. 138 7. The structural unit of complex 1 consists of a [PW12O40]3- ployanion and four 3-PA ligands. In addition, [PW12O40]3- polyanion and 3-PA ligands are linked by H-bonds to form 2-D supramolecular layer. When using as photocatalyst, complex 1 displayed excellent photocatalytic activity towards the reduction of Cr( W) with good structural stability and recyclability. [ABSTRACT FROM AUTHOR]