A　new　series　of　isostructural　lanthanide-based　metal–organic　frameworks,　[H3O][HN(CH3)3]2[Ln3L6]　(Ln=Gd　(1),　Eu　(2),　and　Tb　(3);　H2L=1,3-benzenedicarboxylic　acid),　was　prepared　under　solvothermal　conditions.　Single-crystal　XRD　studies　reveal　that　these　compounds　are　3D　microporous　frameworks　with　1D　channels　distributed　in　four　different　directions.　The　1D　channels　contain　protonated　water　molecules　and　trimethylammonium　cations,　which　can　be　partially　exchanged　with　different　metal　ions.　Notably,　these　compounds　do　not　contain　any　coordinated　solvent　molecules　because　the　coordination　sphere　of　the　Ln3+　ion　is　fully　occupied　by　chelating　and　bridging　carboxylate　oxygen　atoms.　Tunable　colors　and　white-light　emission　can　be　achieved　by　encapsulating　different　molar　ratios　of　Eu3+　and　Tb3+　ions　in　the　Gd　framework　through　cation　exchange.　In　addition,　the　Eu　framework　can　act　as　a　sensitive　and　selective　luminescence　sensor　for　both　Fe2+　and　Fe3+.　©　2016　WILEY-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim