Three-dimensional zigzag Prussian blue analogue and its derivates for bisphenol A scavenging: Inhomogeneous spatial distribution of FeIII in anisotropic etching of PBA

Nanoscale metal-organic frameworks (nano-MOFs) with unique open architectures offer great advantages for constructing fascinating functional materials, but their configurations are largely limited to mesoporous or hollow structures. Both the rational design of nano-MOFs with sophisticated structures and the comprehensive knowledge of their formation mechanism remain an interesting research topic. In this work, we reported a highly peculiar zigzag crystal of a Prussian blue analogue (PBA) bearing the ensemble of walls with uniform thickness (similar to 60 nm) in three-dimensional space. Such Z-like PBA was acquired by the preferential etching of two opposing corners of its parent NiCo-PBA cubes that was pre-doped by metal ligand ions (i. e., [Fe(CN)(6)](3-)). Mechanistic studies suggested that the anisotropic etching seemed to arise from the heterogeneous growth and inhomogeneous spatial distribution of the FeIII and FeII (stemming from redox reaction of FeIII) species, even though all the metal elements (including Fe, Co, and Ni) were evenly dispersed in each individual cube as indicated by HAADF-STEM and linear EDS scan analyses. The open Z structure provided larger surface area and a greater number of active sites to activate reagents in catalytic reaction and enhanced the degradation efficiency in removing bisphenol A from aqueous solution with PMS. The current findings are expected to pave way for a fine tuning the structures and properties of MOFs, and encourage extended research on developing novel anisotropic crystals.