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

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