Symmetry-Breaking Modulated Zr-Metal-Organic Framework Dimensionality for Gradient Acid Sensing with Dual-Phase...

Area of Science:

• Materials Science
• Chemical Sensing
• Nanotechnology

Background:

• Accurate detection of volatile acidic gases and solutions is crucial for industrial safety and environmental monitoring.
• Existing metal-organic framework (MOF) sensors struggle with dual-phase detection, acid discrimination, and mechanistic understanding, limiting their practical use.

Purpose of the Study:

• To design and synthesize a novel two-dimensional (2D) layered zirconium metal-organic framework (Zr-MOF) for efficient and precise dual-phase acid sensing.
• To elucidate the sensing mechanism at the electronic structure level using density functional theory (DFT) calculations.
• To develop a practical sensing device based on the novel Zr-MOF material.

Main Methods:

• Molecular design and synthesis of a quinoxaline-based asymmetric tricarboxylate ligand.
• Construction of a 2D layered Zr-MOF with an open structure.
• Gas-phase and liquid-phase sensing experiments, including colorimetric and fluorescence quenching measurements.
• Density Functional Theory (DFT) calculations to investigate electronic structure changes and sensing mechanisms.
• Fabrication and testing of a flexible Zr-MOF@MF sensing device over multiple cycles.

Main Results:

• The 2D Zr-MOF demonstrated a second-level response to strong acid vapors (e.g., HCl, CF3COOH) with a visible color change.
• The material achieved gradient discrimination of halogen acid strength in the liquid phase via fluorescence quenching (HCl < HBr < HI).
• DFT calculations revealed that acid introduction causes frontier orbital reconstruction and halide ions induce non-radiative transitions and charge transfer pathways, modulating luminescence.
• The flexible Zr-MOF@MF device maintained excellent performance over 15 reversible cycles.

Conclusions:

• The developed 2D Zr-MOF offers a unique dual-phase/dual-mode sensing platform overcoming limitations of traditional 3D MOFs.
• The study provides a clear mechanistic understanding of the acid sensing process at the electronic level.
• The material shows significant potential for next-generation intelligent sensing applications requiring precise recognition and practical usability.