Hydrothermal reaction of phosphomolybdic acid (PMo12) and phosphotungstic acid (PW12) with the surfactant template 1,10-decanediamine (1,10-DAD) yielded two new nanocomposites, [C10H20(NH2)2]2·H3PMo12O40·(H2O)7.5 and [C10H20(NH2)2]2·H3PW12O40·(H2O)2.4. The produced needlelike crystals of the two nanocomposites have fine-layered structures. X-ray diffraction analyses indicate that change of polyoxometallates has little effect on the tilt angle of the 1,10-DAD molecules for such polyoxometallates–organic amine systems. Fourier transform infrared and Raman spectra show that in the hybrid, the PMo12 forms infinite two-dimensional networks, and the PW12 keeps its Keggin structure in the hybrid except distortion to some degree. The two nanocomposites show different photochromic properties; PMo12–DAD hybrid can be colored under ultraviolet irradiation, whereas PW12–DAD hybrid cannot.