Dual‐Catalysis in Copper Tetrahydroxyquinone Drives Super‐Enhanced Cathodic Electrochemiluminescence of Luminol in Neutral Solutions

The development of luminol‐based cathodic electrochemiluminescence (ECL) systems has been hindered by the inherent difficulties of direct electro oxidation of luminol at negative potentials and low conversion efficiency of coreactants to reactive oxygen species (ROS). Additionally, the deprotonation of luminol intermediates requires strongly alkaline condition, restricting its application in bioanalysis. In this work, a facile one‐step synthesized 2D conductive copper tetrahydroxyquinone (Cu─THQ) metal‐organic framework is introduced as a coreaction accelerator into the luminol/H 2 O 2 system, achieving a super‐enhanced efficiency of luminol cathodic ECL in neutral solutionthe ECL signal is amplified by nearly 4500 times with excellent stability. Comprehensive characterizations using electrochemical methods, multiple spectroscopic techniques, and in situ pH monitoring revealed that Cu‐O 4 active sites in Cu‐THQ exhibit a dual‐catalytic mechanism for H 2 O 2 and H 2 O, that is, catalyzing H 2 O 2 to generate abundant ROS and electrolyzing water to provide a localized alkaline microenvironment, thus facilitating ECL of luminol. Theoretical calculation further demonstrated the strong adsorption and catalytic performance of the Cu‐O 4 active center toward H 2 O 2 . Utilizing the strong and stable cathodic ECL of luminol/H 2 O 2 /Cu‐THQ ternary system, a label‐free immunosensor is constructed for ultrasensitive detection of p‐Tau181, an important biomarker for Alzheimer's disease, achieving a detection limit of 4.56 fg −1 .