Node-Activated Persulfate Reduction in a Terbium Metal–Organic Framework for Low-Potential Electrochemiluminescence and Hydroquinone Sensing

Persulfate (S₂O₈^2–)-based electrochemiluminescence (ECL) typically requires high cathodic potentials to activate S₂O₈^2– and often suffers from inefficient utilization of short-lived radical intermediates. Here, we report a terbium metal–organic framework (Tb-CU-10) constructed from Tb₉ secondary building units (SBUs) and a tetratopic pyrene-based ligand (TBAPy), in which coordination-defined nodes facilitate S₂O₈^2– reduction within a reticular nanochannel architecture. Cyclic voltammetry shows that the S₂O₈^2– reduction peak shifts from −1.40 V to −1.17 V, corresponding to a positive shift of approximately 230 mV relative to the free ligand. This modulation of redox energetics lowers the ECL onset potential and enhances emission intensity compared to TBAPy. The confined framework structure further promotes effective interaction between electrochemically generated intermediates. Moreover, the pore dimensions of Tb-CU-10 (∼11 Å) are comparable to the molecular size of hydroquinone (HQ, ∼8 Å), enabling access of HQ to the framework channels and supporting its quantitative ECL detection with dual linear ranges of 0.1–1.5 μM and 1.5 μM–10 mM and a detection limit of 30 nM (S/N = 3). These results demonstrate that coordination-node chemistry can regulate S₂O₈^2– activation and improve ECL efficiency, providing a low-potential sensing platform for phenolic analytes.