Copper and Zinc Metal-Organic Frameworks with Bipyrazole Linkers Display Strong Antibacterial Activity against Both Gram+ and Gram- Bacterial Strains.

Here, we report a new synthetic protocol based on microwave-assisted synthesis (MAS) for the preparation of higher yields of zinc and copper in MOFs based on different bis(pyrazolyl)-tagged ligands ([M(BPZ)] n where M = Zn(II), Cu(II), H 2 BPZ = 4,4'-bipyrazole, [M(BPZ-NH 2 )] n where M = Zn(II), Cu(II); H 2 BPZ-NH 2 = 3-amino-4,4'-bipyrazole, and [M x (Me 4 BPZPh)] where M = Zn(II), x = 1; Cu(II), x = 2; H 2 Me 4 BPZPh = bis-4'-(3',5'-dimethyl)-pyrazolylbenzene) and, for the first time, a detailed study of their antibacterial activity, tested against Gram-negative ( E. coli ) and Gram-positive ( S. aureus ) bacteria, as representative agents of infections. The results show that all MOFs exert a broad-spectrum activity and strong efficiency in bacterial growth inhibition, with a mechanism of action based on the surface contact of MOF particles with bacterial cells through the so-called "chelation effect" and reactive oxygen species (ROS) generation, without a significant release of Zn(II) and Cu(II) ions. In addition, morphological changes were elucidated by using a scanning electron microscope (SEM) and bacterial cell damage was further confirmed by a confocal laser scanning microscopy (CLSM) test.