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

Abstract Achieving the up‐conversion luminescence (UCL) centered around trivalent lanthanide (Ln³⁺) ions in coordination polymers (CPs) is extremely challenging. Herein, Yb³⁺‐doped Ln‐CPs of [Eu_1‐xYb_x(pfbz)₂(phen)Cl] (x = 0.3, namely 3; x = 0.5, namely 4; x = 0.7; namely 5), and [Tb_1‐xYb_x(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.