Pressure-Driven Energy Transfer for Enhanced Red-Light Emission in Europium-Based Metal–Organic Frameworks

Europium-based metal-organic frameworks offer a unique platform for photoluminescent materials due to the tunable ligand structures and the inherent properties of lanthanides. However, their practical applications are limited by low luminescence efficiency due to inefficient ligand-to-metal energy transfer (LMET). Herein, we introduce a pressure-induced hydrogen bond enhancement strategy to promote the LMET process, triggering the bright red light behavior in the initially weakly emitting Eu(BTC)(H₂O)₆ (H₃BTC: benzene-1,3,5-tricarboxylic acid). As the pressure approaches 9.2 GPa, the photoluminescence quantum yield of the sample increases from an initial value of 19.2% to 69.1%. Furthermore, the red-light emission corresponds to CIE coordinates of (0.66, 0.31) at 9.2 GPa, which meets the requirements of the Rec. 2020 display standard. Systematic photophysical characterization results reveal that the enhanced hydrogen bonds effectively optimize intersystem crossing and improve the efficiency of the sensitization process from the ligand antenna to the excited state of Eu³⁺ ions.