Molecular engineering of noncoordinating backbones in Zr-MOFs for ultrasensitive piezofluorochromism-based high pressure sensing

Metal-organic frameworks (MOFs) are promising pressure-responsive luminescent materials, but precise control of their emission under pressure remains a substantial challenge. Here, we engineered the piezofluorochromic response of zirconium-based MOFs by tuning the polarity of the emissive moieties through noncoordinating phenyl substituents. Four isostructural UiO-67 derivatives were synthesized. The most polar ligand, in UiO-67-PA, yields ultrasensitive piezofluorochromism with a bathochromic shift of 190 nanometers per gigapascal below 0.36 gigapascals. This sensitivity arises from two cooperative effects: enhanced conjugation through pressure-driven rotation of the aromatic rings and amplified orbital overlap resulting from polarity-induced electronic redistribution. This work broadens the strategies for modulating MOF luminescence and highlights their potential for pressure sensing.