Negative-Linear-Compressibility-Driven Structural Rigidification Enables High-Efficiency Blue Emission in MIL-116(Al).

Luminescent metal-organic frameworks (MOFs), featuring tunable porous architectures and unique optical properties, hold great promise for applications in bioimaging, fluorescent sensing, and environmental monitoring. However, balancing structural stability, active site density, and emission efficiency in photofunctional MOFs remains highly challenging. Herein, we present a pressure treatment strategy to precisely regulate the local structural environment of MIL-116(Al), thereby enabling efficient blue emission. MIL-116(Al) inherently possesses excellent structural stability and abundant active sites; however, its weak luminescence limits practical applications. Pressure-induced negative linear compressibility results in strengthened hydrogen bonds between uncoordinated carboxyl groups and lattice water molecules. The resulting rigidification suppresses vibrational and rotational motions of aromatic linkers, thereby promoting radiative recombination in MIL-116(Al). Consequently, pressure-treated MIL-116(Al) displays bright-blue emission, with its photoluminescence quantum yield increasing from 4.5% to 60.7%. These results establish a new paradigm for optimizing the performance of photofunctional MOFs with broad implications for optoelectronic applications.