Large Pressure‑Induced Emission Enhancement in Rigid Lanthanide Coordination Polymers

ABSTRACT Lanthanide coordination polymers (Ln‐CPs) hold significant potential for advanced optical applications due to their tunable structures and distinctive emission properties. However, their performance is hindered by the inherently low direct transition efficiency of Ln 3+ ions, which requires optimizing the ligand‐to‐metal energy transfer (LMET) process. Herein, we demonstrate that pressure can enhance the energy transfer efficiencies in two isostructural rigid lanthanide compounds, [Tb(HCOO)(C 2 O 4 )] n and [Eu(HCOO)(C 2 O 4 )] n . Our in‐situ high‐pressure spectroscopy experiments reveal that hydrostatic compression significantly improves their photoluminescence (PL) intensities, with a 15‐ and 12‐fold increase for the terbium and europium compounds, respectively. Synchrotron high‐pressure x‐ray diffraction and first principles calculations reveal the enhanced emission results from pressure‐induced increase in ligand electron delocalization, which effectively lowers the ligands’ excited‐state energy levels. This increases the orbital overlap between the excited states of the ligands and Ln 3+ ions, hence substantially boosting energy transfer efficiency. Additionally, the rigid lattice effectively suppresses thermally activated non‐radiative transitions under high pressure, minimizing energy loss during the energy transfer process. Our findings offer a convenient approach to achieve efficient rare‐earth phosphorescence through pressure management.