Effect of divalent cations on electrochemiluminescence of metal-organic frameworks in bioassay

The structural characteristics of electrochemiluminescent (ECL) microreticula enabled flexible designs for probing specific molecules. However, bioanalysts paid little attention to the impact of concomitant electrolytic carriers on ECL responsiveness of these grids. Our previous finding confirmed the collisional quenching of ECL radiative secondary building units from polarized Br^- and I^-. To further address this concern, herein typical cationic commonplaces including Na⁺, K⁺, Ca²⁺, … in buffer plus regular transition metals - their influences upon the ECL performance of a well-defined zinc porphyrin-organic framework (ZnPOF) were inspected in a one-by-one manner. Except for Na⁺/K⁺, a dozen of divalent metal chlorides exerted an adverse effect in the form of Stern-Volmer quenching on the ECL brightness, which was illuminated to be cation channeling in open voids of ZnPOFs and bonding with O₂-reactive sites as exemplified by the model Ca²⁺ via systematic compositional investigation. Following this principle, a simplistic Ca²⁺-sensitive sensor was developed for quantitative evaluation of health-care calcium supplements with high precision. Above all, this work highlighted the non-negligible interference from those M^n + requisites to the susceptible MOF-based ECL, which should be paid extra attention in bioassays and mechanistic analyses.