Pressure Treatment Induces Structural Symmetry Breaking to Narrow the Bandgap and Enhance Emission in UiO-66

Metal-organic frameworks (MOFs), with a tunable porous structure and unique optical properties, exhibit excellent application potential in photocatalysis, fluorescent sensing, analytical detection, and biomedicine. Among numerous MOFs, UiO-66 is widely studied for its remarkable thermal and chemical stability, yet its optical performance is severely limited by a large bandgap and low charge transfer efficiency. This study proposes a pressure treatment strategy to regulate the conformation of octahedral secondary building units (SBUs) in UiO-66. Pressure treatment disrupts the highly symmetric structure of SBUs, inducing increased orbital overlap and enhanced electronic coupling between the ligands and oxygen atoms within SBUs. Thus, after pressure treatment, the bandgap of UiO-66 is reduced from initial 3.9 to 3.2 eV, and the photoluminescence quantum yield is increased from original 8.0% to 36.7% under ambient conditions. This work provides new insights for improving the optical properties of MOF materials and lays a foundation for expanding their applications.