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, Yb 3 ⁺‐doped Ln‐CPs of [Eu 1‐x Yb x (pfbz) 2 (phen)Cl] (x = 0.3, namely 3 ; x = 0.5, namely 4 ; x = 0.7; namely 5 ), and [Tb 1‐x Yb x (pfbz) 2 (phen)Cl] (x = 0.2, namely 6 ; x = 0.5, namely 7 ; x = 0.6, namely 8 ) are reported by doping Yb 3 ⁺ 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 Eu 3 ⁺ and Tb 3 ⁺ ions, while 5 represents the first instance of an Ln‐CP where the UCL of Eu 3 ⁺ 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 Yb 3 ⁺ ions, marking the first time such a mechanism has been employed in UCL in Eu/Tb‐CPs.