Metal-Organic Frameworks as Tunable Sorbents for Food Sample Preparation

Trace-level chemical contamination across globalized food supply chains demands efficient, selective, and sustainable sample preparation strategies for reliable analytical monitoring. Metal-organic frameworks (MOFs) are crystalline porous materials constructed from metal nodes and multitopic organic linkers that have recently emerged as engineered sorbents capable of complementing conventional extraction media, particularly in terms of selectivity, surface area, and compatibility with green analytical chemistry principles. This review critically examines the deployment of MOFs and MOF-based composites as sorbents across the full spectrum of food sample preparation formats, including solid-phase extraction (SPE), magnetic SPE (MSPE), dispersive SPE (d-SPE), miniaturized variants (pipette-tip SPE, d-μ-SPE), solid-phase microextraction (SPME), stir bar sorptive extraction (SBSE), and QuEChERS-based cleanup. Distinct from prior overviews focused primarily on materials chemistry, this review adopts a food-analysis perspective with an explicit translational lens, distinguishing analytically mature applications from those still at the proof-of-concept stage. The physicochemical properties that govern MOF performance in food matrices, like framework chemistry (Zr, Al, Cr, Zn, Fe, Ln), pore architecture, surface functionality, and hydrolytic stability, are discussed in relation to the predominant extraction mechanisms operative for key contaminant classes, including pesticides, mycotoxins, veterinary drugs, polycyclic aromatic hydrocarbons (PAHs), per- and polyfluoroalkyl substances (PFAS), and heavy metals. Representative applications report recoveries typically within 70-120%, LOQs reaching the ng kg^-1 scale, and RSDs below 10%, with sorbent masses of 3-50 mg and elution volumes as low as 200 μL. The greenness of MOF-based approaches is critically evaluated by consolidating qualitative analytical greenness metric for sample preparation (AGREEprep) indicators across representative studies and explicitly addressing the asymmetry between greener extraction steps and the still-conventional synthesis/activation footprint of most reported MOFs. Practical considerations for routine laboratory implementation, including reusability, synthesis scalability, matrix fouling, and regulatory compliance with SANTE guidelines, are critically assessed. Finally, priority research directions are identified, encompassing mechanochemical and deep eutectic solvent-assisted MOF synthesis, food-grade biocompatible MOFs, and integration into online SPE and lab-on-chip platforms, to bridge materials science and routine food safety monitoring.