Tuning the electronic structure and hydrophilicity of Prussian-blue type catalysts by incorporation of alklypyrazinium bromides, for enhanced activity

Prussian blue (PB) type material, a historical metal coordination material, is widely used in batteries, catalyst, and for energy storage. However, the scarcity of active sites and its immutable structure limit further applications. Herein, we propose a ligand substitution strategy to tune the electronic structure and hydrophilicity of the PB-type material, involving Fe(CN)5 as a cyanide precursor, to catalyze epoxidation of olefins. The catalytic performance can be significantly promoted for styrene oxide in the presence of a CoFe PB analog that includes decylpyrazinium bromide (named CoFe-10). Kinetic studies on styrene epoxidation with CoFe-10 show a low activation energy of 27.2 kJ/mol. In addition, mechanistic investigation, coupled to electron paramagnetic resonance (EPR) measurements, suggests that the CoOOC(CH3)3 adduct is the reactive species for epoxidation of styrene. This study provides an effective strategy to synthesize unprecedented PB-type material and extend its application. [Display omitted] •The symmetry and hydrophobicity of CoFe Prussian blue analogues were altered significantly by ligand substitution.•The reaction order of epoxidation of styrene were determined.•A competitive apparent activation energy (Ea) for CoFe-10, 27.2 kJ/mol, was obtained.