Achieving Bright Up-Conversion Luminescence of Eu3+ and Tb3+ Ions within Coordination Polymers

Achieving the up-conversion luminescence (UCL) centered around trivalent lanthanide (Ln(3+)) ions in coordination polymers (CPs) is extremely challenging. Herein, Yb3+-doped Ln-CPs of [Eu1-xYbx(pfbz)(2)(phen)Cl] (x = 0.3, namely 3; x = 0.5, namely 4; x = 0.7; namely 5), and [Tb1-xYbx(pfbz)(2)(phen)Cl] (x = 0.2, namely 6; x = 0.5, namely 7; x = 0.6, namely 8) are reported by doping Yb3+ into Ln-CPs of [Ln(pfbz)(2)(phen)Cl] (Ln = Eu, 1; Ln = Tb, 2). Both 5 and 8 visually exhibit excellent cooperative sensitization UCL of Eu3+ and Tb3+ ions, while 5 represents the first instance of an Ln-CP where the UCL of Eu3+ ion is visually observable. Investigations into the UCL of these CPs reveal that the energy transfer is achieved through direct energy transfer from two individual Yb3+ ions, marking the first time such a mechanism has been employed in UCL in Eu/Tb-CPs.