Two novel isostructural polyoxometalate (POM)-based metal-organic frameworks (MOFs) with diamond topology, NENU-506 and NENU-507, were hydrothermally synthesized. They not only combine the advantages of both POMs and MOFs, but also show excellent chemical and thermal stability. Notably, NENU-507 exhibited a high reversible capacity of 640 mA h g-1 after 100 cycles when applied as an anode material in lithium-ion batteries.