Cu and Zn MOFs with bipyrazole linkers to prevent antimicrobial decay of climacteric fruits during the storage / transportation steps

Microbial infections in agricultural production have a significant impact on the economies of developed nations and even more so in underdeveloped countries. It is estimated that food waste amount ∼ 33–50% of global manufactured food spoils as consequence of microbial contamination during the storage/transport phases of supply chain. Metal-Organic Frameworks (MOFs) are emerging nanomaterials with largesurface networks, regular porosity and good structural rigidity. They are attracting growing interest for antimicrobial applications due to their poor solubility in water and organic solvents, which allows their use in solid composite materials as antimicrobial additives. Here we report a detailed study of the antimicrobial activity of some Zn(II) and Cu(II) MOFs with bipyrazole linkers against gram-positive (S. aureus) and gram-negative (E. coli) bacterial strains, as well as fungal strains P. citrinum, P. expansum, C. gloeosporioides and M. piriformis that typically attack climacteric fruits after harvesting. Mainly Zn-MOFs show a broad spectrum activity and strong efficiency in inhibiting microbial growth, and an in-depth study has also allowed us to hypothesize their mechanism of action based on surface contact of MOFs nanoparticles with microbes through the so-called “chelation effect” and reactive oxygen species (ROS) generation