Lanthanide　ion　contained　metal-organic　frameworks　(MOFs)　have　garnered　significant　attention　in　the　fields　of　solid-state　lighting　and　chemical　sensing　due　to　their　porous　structure　and　distinctive　optical　properties.　However,　they　also　present　challenges　because　of　the　limited　photoluminescence　(PL)　intensity　resulting　from　the　parity-forbidden　f-f　transitions　of　lanthanide　ions.　Herein,　the　study　reports　a　new　heterometallic　MOFs　Ln3Li2L4　(Li-Ln-MOF,　Ln　=　Y,　Eu,　Tb　and　Dy,　L　=　deprotonated　1,3,5-tris(4-carboxyphenyl)benzene)　with　a　Brunauer-Emmett-Teller　(BET)　surface　area　of　774.1　m2/g.　The　porous　crystal　structure　of　Li-Ln-MOF　is　characterized　by　three　kinds　of　channels　interpenetrating　with　each　other.　By　employing　ligand　alternation　and　lanthanide　ion　alloying　strategies,　Li-Y1-xEux-MOF1　crystal　isostructural　with　Li-Ln-MOF　is　synthesized　by　using　2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine　(H3TATB)　as　ligand.　The　Li-Y0.7Eu0.3-MOF1　crystal　excels　in　the　comprehensive　performance　with　a　BET　surface　area　of　858.8　m2　g-1　and　a　near-unity　PL　quantum　yield.　The　time　density　functional　theory　and　natural　transition　orbitals　calculations　unravel　that　the　outstanding　optical　properties　Li-Y0.7Eu0.3-MOF1　originates　from　the　charge　transfer　between　TATB3-　and　Eu3+.　Benefiting　from　the　excellent　comprehensive　performance　of　Li-Y1-xEux-MOF1,　the　study　reveals　their　potentials　as　single-composition　white-light　emission　and　fluorescent　sensing　probe　for　the　detection　of　nitrobenzene.　A　strategy　via　ligand　alteration　is　developed　to　achieve　a　near-unity　photoluminescence　quantum　yield　in　lanthanide　metal-organic　frameworks　(Ln-MOFs)　with　a　porosity　of　up　to　53.6%.　Mechanistic　investigation　through　theoretical　calculation　and　time-resolved　spectra　unravel　that　Ln-MOF　displayed　outstanding　optical　properties　ascribed　to　the　charge　transfer　from　the　triple　excited　state　of　ligand　to　the　Ln3+.　image