Yb³⁺-Induced Bright Ligand Up-Conversion Luminescence in 1D Coordination Polymers

Ln³⁺-induced ligand up-conversion luminescence (UCL) in coordination polymers (CPs) effectively overcomes the inherent limitations of conventional organic UCL mechanisms. However, current research on UCL in Ln-CPs has predominantly focused on the UCL of Ln³⁺ ions themselves, while investigations into Ln³⁺-induced ligand UCL is overlooked in Ln-CPs. Herein, by doping Yb³⁺ into the Ln-CPs of [Y₂(FCA)₆]_n 1) (FCA = 9-fluorenone-2-carboxylic acid), Yb³⁺-doped 1D chain Ln-CPs of [Y_2-2xYb_2x(FCA)₆]_n (x = 0.2, 2) x = 0.5, 3) x = 0.7, 4) x = 0.9, 5) x = 1, 6) are prepared. Investigation of the UCL of FCA in these CPs reveals that Ln³⁺-induced ligand UCL are achieved for the first time. Notably, 4 not only displays bright UCL under both 10 and 15 W cm^-2 excitation power of 980 nm laser but also achieves an absolute UCQY of 0.003 %, opening new avenues for the development of Ln-CPs as UCL materials.