关键词: 四氧化三铁, 金属有机框架, 磁性纳米复合材料, 磁性固相萃取

Abstract: Sample pretreatment is a critical step in analytical chemistry, directly affecting the accuracy and reliability of analytical results. Traditional methods such as liquid-liquid extraction and solid-phase extraction suffer from high organic solvent consumption, complicated procedures, and limited selectivity. Magnetic solid-phase extraction (MSPE), as a novel pretreatment technology, has attracted extensive attention due to its simple operation, rapid separation, and minimal solvent consumption. MSPE involves adsorption, magnetic separation, washing, and elution steps, where magnetic adsorbents are quickly separated from sample matrices under an external magnetic field, eliminating centrifugation or filtration steps. Among various magnetic materials, Fe₃O₄ nanoparticles are the most commonly used magnetic carriers due to their low cost, high magnetic responsiveness, and good biocompatibility. However, Fe₃O₄ nanoparticles have inherent drawbacks such as small specific surface area, limited active sites, and poor adsorption selectivity. Metal-organic frameworks (MOFs), formed by self-assembly of metal ions with organic ligands, possess high specific surface area, tunable pore structure, rich surface chemistry, and excellent stability. MOFs have shown great potential in gas adsorption, catalysis, sensing, and sample pretreatment as excellent adsorbents. However, MOF materials face challenges such as difficult separation and poor reusability. The combination of Fe₃O₄ and MOFs leverages their synergistic advantages. MOFs provide abundant active sites for adsorption, while Fe₃O₄ endows the composite with rapid magnetic separation capability. This composite solves the recovery difficulty of MOFs and overcomes the limitations of Fe₃O₄ in adsorption capacity and selectivity. Magnetite/metal-organic framework (Fe₃O₄/MOF) composites combine the superparamagnetism of Fe₃O₄ with the high specific surface area and tunable pore structure of MOFs, emerging as promising materials for sample pretreatment. This review systematically summarizes four main preparation strategies: one-pot method, in-situ growth method, post-synthetic modification method, and layer-by-layer assembly method. The interfacial binding mechanisms, structural controllability, and practical application performance of each method are analyzed in detail. On this basis, the application progress of Fe₃O₄/MOF composites in sample pretreatment is comprehensively reviewed, covering food analysis, biological samples, environmental water monitoring, cosmetics testing, and forensic toxicology. Despite their promising prospects, different preparation methods yield materials with varying MOF loading uniformity and cyclic stability. Long-term performance validation in complex matrices remains insufficient. Current research issues include uneven MOF loading, harsh preparation conditions, limited reusability cycles, and inadequate performance verification. Future research should focus on developing adsorbents with simple synthesis, controllable structure, high selectivity, and good reusability. Promoting online coupling of sample pretreatment with detection instruments will also be a key step toward practical application. This review provides a reference for related fields by systematically summarizing the preparation strategies and application progress of Fe₃O₄/MOF composites.

Key words: magnetite (Fe₃O₄), metal-organic frameworks (MOF), sample pretreatment, magnetic solid phase extraction