New MXene-derived anthracene-based metal–organic framework with controllable morphology for high-performance sensing

Abstract

Morphological variations in metal–organic frameworks (MOFs), such as differences in shape and size, critically influence their properties, including surface area, mechanical strength, and optical behaviour. These morphological features are often controlled by synthetic parameters, thereby directly affecting MOF performance in applications such as catalysis and sensing. In this study, we present a novel approach in which MXenes are used as a metal precursor to synthesize MOFs with ultrathin two-dimensional (2D) nanosheet morphologies, offering promising potential for device integration. Specifically, we synthesized an anthracene-based vanadium MOF (V–A MOF) with two distinct morphologies: bulk nanorods derived from VOSO₄ as the metal precursor (VOSO₄–A MOF) and ultrathin nanosheets derived from V₂C MXene as the metal precursor (V₂CT_x–A MOF). The combination of π-conjugated anthracene ligands and redox-active vanadium centers yields strong fluorescence emission. Structural analyses confirmed successful synthesis and morphology control. Both MOFs were evaluated as optical sensors for detecting metal ions and nitroaromatic compounds. Photoluminescence studies revealed highly sensitive and selective fluorescence quenching toward Fe³⁺ and Pb²⁺ ions, with the V₂CT_x–A MOF nanosheets demonstrating up to a sixfold enhanced response compared with that of the bulk nanorods. Mechanistic investigations, supported by spectroscopic techniques and density functional theory (DFT) calculations, indicate that fluorescence arises from linker-to-metal charge transfer, whereas sensing predominantly occurs via Förster resonance energy transfer. This work highlights the profound impact of the framework structure and nanoscale morphology on the accessibility of active sites and overall sensing efficiency, emphasizing the advantages of MXene-derived nanosheets in enhancing MOF-based sensor performance.