An　all-inorganic　three-dimensional　(3D)　polyoxoniobate　(PONb)　framework,　Na6K4[(Nb6O19)CrIII(H2O)2]2·38H2O　(1)　has　been　synthesized　via　the　hydrothermal　method.　The　fundamental　building　unit　of　[(Nb6O19)CrIII(H2O)2]210−　is　connected　by　K+　ions,　forming　a　3D　framework　structure　with　channels　along　the　b-axis.　Compound　1　exhibits　good　thermal　stability,　and　selectively　absorbs　Co2+　ions　while　excluding　Ni2+　ions　from　acetonitrile　solutions,　PXRD　analysis　confirms　that　its　framework　remains　intact　after　adsorption,　indicating　its　potential　as　an　effective　ion-exchange　material.　©　2024　Elsevier　Inc.