Interfacial Electronic Modulation in MXene–COF Nanostructures for Reversible Room-Temperature Hydrogen Sensing

Real-time hydrogen detection under ambient and portable conditions is often hindered by the inherent trade-off between strong adsorption for sensitivity and weak interaction for rapid reversibility in porous semiconductor materials. In this work, a redox-active anthraquinone-based covalent–organic framework (DAAQ-COF) interfaced with conductive Ti3C2 MXene enables enhanced interfacial charge transfer, simultaneously modulating hydrogen adsorption across the large accessible surface area. The optimized DAAQ@Ti3C2-50 flexible sensor detects hydrogen (1 ppm) at room temperature, exhibiting response (Tres) and recovery times (Trec) of 29 and 18 s, respectively, with ∼99.9% signal reversibility. Stable sensing behavior is preserved under high bending deformation (97.45°; 85/87 s; 99.9%) and at 150 °C (74/88 s; 99.5% recovery), indicating structural integrity and sustained electronic interactions under mechanical and thermal stress. Density functional theory calculations reveal weak H2 physisorption on pristine DAAQ-COF (−0.051 eV) and strong chemisorption on Ti3C2 (−1.91 eV), whereas the heterointerface promotes optimized hydrogen adsorption accompanied by charge redistribution. These results establish interfacial-modulation adsorption as a viable route toward high-sensitivity yet fully reversible hydrogen sensing platforms.