MOF-on-MOF heterostructured composites for food safety analysis: construction strategies, sensing applications and sample pretreatment

Abstract

Food safety requires rapid, sensitive and reliable methods for detecting contaminants in complex food matrices. Metal–organic frameworks (MOFs), owing to their high surface areas, tunable pores and abundant functional sites, have shown considerable potential in food sensing and sample pretreatment. Recently, MOF-on-MOF heterostructures have attracted increasing attention because their hierarchical architectures and tunable interfaces can integrate complementary adsorption, catalytic and signal-transduction functions. This review summarizes the major construction strategies and structural types of MOF-on-MOF materials, with emphasis on epitaxial growth, seed-mediated assembly, interfacial engineering and post-synthetic conversion. Particular attention is given to the distinction between intact MOF-on-MOF heterostructures, MOF-on-MOF-derived materials and related MOF-based hybrids. Recent applications in electrochemical and optical sensing, biosensing-related platforms, and sample pretreatment by magnetic solid-phase extraction (MSPE), solid-phase microextraction (SPME) and dispersive micro-solid-phase extraction (DµSPE) are critically reviewed, together with emerging applications in food preservation and freshness monitoring. Structure–function relationships and analytical performance are discussed beyond sensitivity alone, considering matrix effects, selectivity, reproducibility and stability. Finally, current challenges in mechanistic understanding, material safety, batch-to-batch consistency and scalable fabrication are highlighted. Future priorities include robust real-matrix validation, reproducible synthesis, portable multimodal analysis and more sustainable fabrication, providing guidance for the practical development of MOF-on-MOF materials in food-safety analysis.