Matrix Coordination-Induced Electrochemiluminescence Enhancement of Tetraphenylethylene-Based Hafnium Metal–Organic Framework: An Electrochemiluminescence Chromophore for Ultrasensitive Electrochemiluminescence Sensor Construction

Abstract

Here, we discovered that rigidifying the tetraphenylethylene (TPE)-based ligand H₄TCBPE (H₄TCBPE = 1,1,2,2-tetra(4-carboxylbiphenyl)ethylene) into Hf-based metal-organic framework (Hf-TCBPE) could lead to a stronger electrochemiluminescence (ECL) emission in comparison to H₄TCBPE aggregates and H₄TCBPE monomers. Due to the lack of close-packed TCBPE chromophores in Hf-TCBPE, which was required for aggregation-induced ECL (AI-ECL) enhancement, we defined this unprecedented phenomenon as matrix coordination-induced ECL (MCI-ECL) enhancement. The strong ECL intensity of Hf-TCBPE not only originated from the fixation of the TCBPE ligand between Hf₆ clusters that restricted the intramolecular free motions of TCBPE and suppressed the nonradiative relaxation but also stemmed from the high porosity of Hf-TCBPE that rendered both internal and external TCBPE chromophores able to be excited. Considering the unique ECL characteristic of Hf-TCBPE, we combined the new ECL indicator of Hf-TCBPE as well as the phosphate-terminal ferrocene (Fc)-labeled hairpin DNA (Fc-HP3) aptamer together as a signal probe (Hf-TCBPE/Fc-HP3), which was employed to construct a novel "off-on" ECL sensor for ultrasensitive mucin 1 (MUC1) detection with the assistance of the exonuclease III (Exo III)-assisted recycling amplification strategy. As expected, the ECL sensor displayed a desirable linear response range from 1 fg/mL to 1 ng/mL and the detection limit down to 0.49 fg/mL. The MCI-ECL enhancement demonstrated by the Hf-TCBPE developed a new and promising strategy to design and synthesize high-performance metal-organic framework (MOF)-based ECL materials for constructing ultrasensitive ECL sensors.