Porous by design, rich by function: Covalent organic frameworks as emerging materials for food safety and smart packaging

Global food security faces a dual crisis: postharvest losses of fruits and vegetables that reach up to 55% of total production annually, and persistent contamination with pesticides, mycotoxins, heavy metals, and pathogenic microorganisms, threatening public health worldwide. Conventional detection and preservation strategies remain insufficient in sensitivity, speed, multifunctionality, and sustainability. Covalent organic frameworks (COFs), which are intrinsically metal-free crystalline porous materials constructed from light organic elements via strong covalent bonds, together with their functionalized metal-containing composites, have emerged as a structurally versatile platform for addressing these challenges. Distinguished from conventional porous materials by ultra-high specific surface areas, tunable pore geometries, outstanding thermal and chemical stability, and rich surface functionalizability, COFs avoid the metal-node leaching pathway intrinsic to MOFs, although their comparative suitability for food contact remains to be established by systematic migration testing. This review examines COF roles in food science through a structure-property-function framework, treating linkage chemistry, pore architecture, donor-acceptor band engineering, and synthesis route as four coupled design levers from which food-safety applications are systematically derived. Four interconnected domains are covered: (i) COF-based solid-phase extraction sorbents and biosensing platforms for ultrasensitive detection of mycotoxins, pesticides, heavy metals, and foodborne pathogens; (ii) stimulus-responsive intelligent packaging and antibacterial composite films for postharvest preservation of fruits, vegetables, meat, and seafood; (iii) photocatalytic, contact-mediated, and synergistic antibacterial mechanisms; and (iv) COF nanozymes as dual-function platforms for simultaneous toxin detection and catalytic degradation. Key barriers to scalable synthesis, regulatory approval, and long-term stability in food matrices are critically evaluated, and future directions are charted, including linkage hydrolysis kinetics, AI-assisted COF design, and biodegradable composites.