Functional Nanozymes Consisting of Co2+-ZIF-67 Metal-Organic Framework Nanoparticles and Co2+-ZIF-67/Polyaniline Conjugates

Abstract

Co2+-ZIF-67 metal-organic framework nanoparticles (NMOFs), act as nanozymes catalyzing diverse processes, including peroxidase, oxidase, and catalase activities. Peroxidase activities are reflected by the nanozyme-catalyzed H2O2 oxidation of dopamine to aminochrome, the H2O2 oxidation of NADH to NAD+, the H2O2-catalyzed generation of chemiluminescence through oxidation of luminol, and the H2O2-mediated oxidation of aniline to polyaniline. Oxidase activities of the nanozyme are demonstrated by the Co2+-ZIF-67 NMOFs catalyzed aerobic oxidation of dopamine to aminochrome and of NADH to NAD+, and catalase activities of the nanozyme are reflected by the catalytic decomposition of H2O2. Moreover, the Co2+-ZIF-67 catalyzed oxidation of aniline to polyaniline (PAN) by H2O2 is accompanied by the coating of NMOFs with PAN to yield a Co2+-ZIF-67/PAN hybrid material. Coating the particles in the presence of guest substrates leads to molecular imprinted PAN matrices revealing enhanced ZIF-67 catalyzed transformations as compared to non-imprinted PAN matrices. This is demonstrated by imprinting of 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid), ABTS2−, in the PAN coating and the 3.3-fold enhanced catalyzed oxidation of ABTS2− by H2O2, as compared to the non-imprinted PAN hybrid composite. Moreover, imprinting of L-/D-DOPA in the PAN coating of Co2+-ZIF-67 NMOFs leads to chiro-selective H2O2-guided oxidation of L-/D-DOPA to dopachrome by the NMOFs/PAN composite.