Fewer-layer conductive metal-organic Langmuir-Blodgett films as electrocatalysts enable an ultralow detection limit of H2O2

Highlights: • A simple and scalable method to prepare conductive metal-organic LB films. • A new record of H₂O₂ detection limit based on the non-precious LB films (10⁻¹⁰, m/m). • Quick response, good sensitivity, high stability, and perfect reproducibility. • Reaction mechanism and electron transfer processes at the internal interfaces. The detection of low-concentration hydrogen peroxide (H₂O₂) has important theoretical-significance and practical value in many fields, such as medical science, biological chemistry, and food safety inspection. Traditional commercial H₂O₂ test paper and detection technology can only reach the detection limit of 10⁻³–10⁻⁵ (mass fraction). In this paper, we report a simple method to prepare 2D MOF (metal-organic frameworks) [Co₃(HOB)₂]_n films based on Langmuir-Blodgett (LB) method combined with layer-by-layer growth technique. Even 3-layer [Co₃(HOB)₂]_n films can realize the lowest H₂O₂ detection limit of 1.05 × 10⁻⁸ wt% (3.08 nmol·L⁻¹) based on the resultant 2D MOF catalyst. Meanwhile, density functional theory (DFT) calculations revealed that Co²⁺ ions of the LB films decreased the energy of [HOOH] transforming into [HO₂] during the H₂O₂ reduction reactions, thus speeding up the decomposition of H₂O₂.