A new compound NH4Co2OH(MoO4)2⋅H2O was prepared by precipitation of aqueous solutions of cobalt nitrate and ammonium heptamolybdate at pH = 7.5. The crystal structure was identified by X-ray powder diffraction (XRPD) and Rietveld refinement as a known polymorph of layered molybdates (Φy) with general formula AT2OH(MoO4)2⋅H2O (A = NH4+, Na+, K+ and T = Zn2+, Co2+, Cu2+, Ni2+) and refined from a model based on that structure. The lattice parameters were refined with R-3 space group (148) a = 6.1014(2) Å, b = 6.1014(2) Å, c = 21.826(1) Å, α = 90°, β = 90°, and γ = 120°.
