Lithium‐Lanthanide Heterometallic Organic Frameworks with Near‐Unity Photoluminescence Quantum Yields for Single‐Composition White‐Light Emission and Fluorescent Sensing on Nitrobenzene

Abstract 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‐Y_1‐xEu_x‐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‐Y_0.7Eu_0.3‐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‐Y_0.7Eu_0.3‐MOF1 originates from the charge transfer between TATB³⁻ and Eu³⁺. Benefiting from the excellent comprehensive performance of Li‐Y_1‐xEu_x‐MOF1, the study reveals their potentials as single‐composition white‐light emission and fluorescent sensing probe for the detection of nitrobenzene.