The high speed of contaminants growth needs the burgeoning of new analytical techniques to keep up with the continuous demand for monitoring and legislation on food safety and environmental pollution control. Metal-organic frameworks (MOFs) are a kind of advanced crystal porous materials with controllable apertures, which are self-assembled by organic ligands and inorganic metal nodes. They have the merits of large specific surface areas, high porosity and the diversity of structures and functions. Latterly, the utilization of metal-organic frameworks has attracted much attention in environmental protection and the food industry. MOFs have exhibited great value as sensing materials for many targets. Among many sensing methods, fluorometric sensing is one of the widely studied methods in the detection of harmful substances in food and environmental samples. Fluorometric detection based on MOFs and its functional materials is currently one of the most key research subjects in the food and environmental fields. It has gradually become a hot research direction to construct the highly sensitive rapid sensors to detect harmful substances in the food matrix based on metal-organic frameworks. In this paper, we introduced the synthesis and detection application characteristics (absorption, fluorescence, etc.) of metal-organic frameworks. We summarized their applications in the MOFs-based fluorometric detection of harmful substances in food and water over the past few years. The harmful substances mainly include heavy metals, organic pollutants and other small molecules, etc. On this basis, the future development and possible application of the MOFs have prospected in this review paper.
A rapid method was developed to determine the content of tyramine in food on the basis of the combination of molecular imprinting technique and the metal-organic frameworks. We developed the new molecular imprinted polymers based on metal-organic frameworks UiO-66 (named UiO-66@MIPs) as the sensing recognition element, the non-molecular imprinted polymers based on UiO-66 (named UiO-66@NIPs) was synthesized according the same steps without tyramine for comparison. The characterization of obtained UiO-66@MIPs was investigated through a series of characterization experiments. The results indicated that the octahedral shaped UiO-66 was encapsulated in the sol-gel polymer film, with a desirable thermal stability and possessed a specific surface area (SSA) of 994.3 m2·g−1. The imprinting factor of the UiO-66@MIPs for tyramine was 1.956 in static experiment. This indicates the synthesized UiO-66@MIPs have outstanding performance compered to UiO-66@NIPs on the static adsorption quantity and selective adsorption affinity. It’s to make use of advantages of the synthetic materials to develop a quartz crystal microbalance (QCM) sensor for the sensitive detection of tyramine. The detection limit of the system was 61.65 μg·L−1 within measurable concentration range from 80 to 500 μg·L−1. The prepared QCM sensor was verified in selectivity and application. The UiO-66@MIPs possess good behavior on selectivity, absorptivity, and chemical stability, so the UiO-66@MIPs achieve accurate and rapid trace detection of biogenic amines in food combining with the quartz crystal microbalance.
Functional nanoprobes which detect specific food hazards quickly and simply are still in high demand in the field of food-safety inspection research. In the present work, a dual-emission metal-organic framework-based ratiometric fluorescence probe was integrated to detect Cu2+ and Pb2+ with rapidness and ease. Specifically, quantum dots (QDs) and carbon quantum dots (CQDs) were successfully embedded into zeolitic imidazolate framework-67 (ZIF-67) to function as a novel ratiometric fluorescent sensing composite. The ratiometric fluorescence signal of CQDs/QDs@ZIF-67 was significantly aligned with the concentration of metal ions to give an extremely low detection limit of 0.3324 nM. The highly sensitive and selective CQDs/QDs@ZIF-67 composite showed potential for the rapid and cost-effective detection of two metal ions.
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