Probing the Formation of Metal–Organic Cages by Electrochemiluminescence

It is important to probe the formation of metal-organic cages (MOCs) to ensure their versatility. Currently, the formation of MOCs is commonly characterized by using single-crystal X-ray diffraction, mass spectrometry, and nuclear magnetic resonance. However, the application scopes of these techniques are limited because they require that MOCs have high-quality single crystals, excellent solubility, and superior stability. In this work, we introduced an electrochemiluminescence (ECL) method to rapidly probe the formation of palladium-based MOCs. It was demonstrated that the formation of the Pd₂L₄ MOCs could lead to a significant increase in charge transfer resistance and a noticeable change in surface charge, resulting in substantial quenching (up to 99.1%) of the ECL signal in the Ru(bpy)₃²⁺/tripropylamine (TPA) system. This innovative "signal-off" ECL sensing mechanism allowed for a fast and ultrasensitive identification of MOC formation. Our findings not only provide a robust strategy for rapid characterization of supramolecular assemblies but also open new avenues for extending ECL-based analytical techniques to the study of other crystalline materials.