Synergistically Functioning Cobalt and Zinc Active Centers from the Pyrolysis of Their Bimetallic ZIFs Exhibiting Orders-of-Magnitude Higher Organophosphorus Hydrolase-Mimicking Activity than Either One Alone.

In the biological world, either zinc or cobalt acts as an enzymatically active center for organophosphorus hydrolase (OPH), where OPH functions as a dimer with two identical Zn-Zn or Co-Co atomic centers with an appropriate distance and surrounding microenvironment, thereby working synergistically. In this work, cobalt and zinc sub-nanometer particles were co-dispersed in a carbon matrix by the pyrolysis of their bimetallic ZIF precursors with an appropriate ratio of Co2+/Zn2+. The specific OPH-mimicking activity of co-dispersed and synergistically functioning cobalt and zinc sub-nanoparticles per mg of the combined Co and Zn can reach orders-of-magnitude higher (up to 50 times) than that of cobalt or zinc nanoparticles alone per mg of Co or Zn in the same matrix. It was Co doping for Zn-based ZIF precursors and zinc's partial evaporation during the pyrolysis that resulted in both highly dispersive cobalt and zinc bimetallic active centers with sizes of sub-nanometers or nearly in the level of single atoms, partially mimicking the interaction of the two metal centers of the biological OPH dimer and thus the synergistically functioned and profoundly boosted OPH-mimicking activities.