Layered Mn-MOF modified with carbon quantum dots for efficient detection of trace hydrogen peroxide in beverages

Developing high-sensitivity hydrogen peroxide (H₂O₂) sensors is crucial. Metal organic frameworks (MOFs) are considered one of the ideal materials for developing H₂O₂ sensors for their adjustable pore size and diverse topological structures. In this work, solvothermal synthesis is utilized CQD@Mn-MOF using carbon quantum dots (CQDs) and two-dimensional Mn-MOF ([Mn(Tib)(H₂O)₃]·(TPA)·3H₂O, Tib = 1,3,5-triamidazolylbenzene, TPA = terephthalic acid) as precursors. Interestingly, CQD@Mn-MOF as an electrochemical sensor can effectively detect H₂O₂ with a lower detection limit of 14.7 μM, and higher sensitivity (approximately 5 times that of pure Mn-MOF). CQD@Mn-MOF sensor is capable of detecting H₂O₂ with high selectivity in the presence of other interfering agents such as proline, ascorbic acid, glucose, and various metal salts. In addition, CQD@Mn-MOF electrochemical sensor has been used to effectively determine the H₂O₂ content in actual beverages such as fruit juice and beer. The sensing mechanism has been reasonably analyzed that the MnO₂ produced by Mn²⁺ + H₂O₂ = MnO₂ + 2H⁺ reaction acts as a specific catalyst for H₂O₂ decomposition reaction (MnO₂ + H₂O₂ + 2H⁺ = Mn²⁺ + O₂ + 2H₂O). This sensing mechanism further ensures the high selectivity of the sensor for H₂O₂. Significantly, the introduction of CQD not only improves the conductivity of Mn-MOF, but also can provide more active sites in the catalytic reaction, improve the contact area and reaction rate of the reaction, and improve the catalytic performance of Mn-MOF, further improve the sensitivity.