A　novel　inorganic-organic　hybrid　polyoxoniobate　framework　based　on　crescent-like　{SiNb18O54}　building　blocks　and　[Cu(en)](2+)/K+　(en　=　ethylenediamine)　linkers　has　been　successfully　made　under　hydrothermal　condition.　The　compound　is　very　stable　under　various　conditions,　and　can　selectively　absorb　crystal　violet　from　aqueous　solution.　Additionally,　the　proton-conduction　property　of　the　compound　was　also　studied.