A　water-soluble　niobium-citrate-peroxo　compound　was　synthesized　by　using　Nb2O5　as　a　precursor.　This　niobium　compound　solution　was　successfully　applied　to　the　preparation　of　microcrystalline　ZnNb2O6　photocatalysts　via　a　water-based　sol-gel　method.　The　results　indicated　that　pure　ZnNb2O6　could　be　obtained　in　a　temperature　range　from　750　to　950　degrees　C.　The　absorption　edge　of　ZnNb2O6　located　at　about　305　nm,　corresponding　to　a　band　gap　of　ca.　4.06　eV.　The　photocatalytic　activities　of　the　as-prepared　samples　for　the　methyl　orange　degradation　were　evaluated　under　UV　light　(lambda　=　254　nm).　It　was　found　that　the　sample　obtained　at　850　degrees　C　showed　the　highest　photocatalytic　activity　due　to　its　suitable　surface　area　and　crystallinity.　(C)　2011　Elsevier　Masson　SAS.　All　rights　reserved.