Retrieving the Stability and Practical Performance of Activation‐Unstable Mesoporous Zr(IV)‐MOF for Highly Efficient Self‐Calibrating Acidity Sensing

Abstract The practical applications of activation‐unstable mesoporous metal‐organic frameworks (MOFs) are often constrained by their structural instability. However, enhancing their stability could unlock valuable functionalities. Herein, we stabilized the otherwise unstable, post‐activated structure of a novel mesoporous Zr(IV)‐MOF, NKM‐809, which constructed from a pyridine‐containing amphiprotic linker (PPTB). We applied two strategies: mixed‐linker synthesis and linker installation. In the mixed‐linker approach, we incorporated an auxiliary linker, TPTB, which resembles PPTB, during synthesis to improve the framework's stability. In the linker installation approach, we introduced a ditopic carboxylate linker (BPDC) into the coordination‐unsaturated sites of NKM‐809. These strategies produced stabilized derivatives, named NKM‐808.X (X=χ PPTB ) and NKM‐809‐BPDC, which exhibit pH‐responsive dual‐wavelength fluorescence at distinct emission wavelengths. Remarkably, these emissions shift oppositely upon protonation and dissociation, distinguishing them as highly sensitive, self‐calibrating acidity sensors. In NKM‐809‐BPDC, an additional quenching of the linker‐emission (419 nm) minimizes inherent interference, enabling integrated quality and lifespan self‐monitoring. Theoretical calculations identified transitions between (n, π*) and (π, π*) emission states during the sensing process and highlighted the role of a stable mesoporous network in achieving stronger protonation response. These findings showcase the potential of stabilized mesoporous MOFs for practical applications, alongside valuable insights into strategies for optimizing such materials.