Macrosphere-supported nanoscale Prussian blue analogues prepared via self-assembly as multi-functional heterogeneous catalysts for aqueous oxidative and reductive reactions

While Prussia Blue analogues (PBs) are promising catalysts, PBs are typically prepared to be nanoscale, making them less practical especially for solution-based reactions. Although a few attempts have developed substrate-supported PBs, many of them are still very small and PB is not grown homogeneously. However, there is still an urgent demand for developing substrate-supported PB which is catalytically effective, convenient-to-prepare, simple-to-use and easy-to-recover. To this end, a macrosphere-supported nanoscale PB is proposed using ion exchange resins as readily available, robust and functionalized macrospheres. Through layer-by-layer impregnating resins in cobalt and hexacyanoferrate solutions, PB is grown on the surface of resins via self-assembling. Both cation and anion exchange resins (CR and AR) can be successfully employed to grown PB through the same self-assembling technique. The resulting PB@R can preserve porous structures and metal coordination of PB, and easy-to-handle features of resins, making them promising catalysts for aqueous catalytic reactions. As 4-NP reduction is selected as a model reductive reaction, PB@R quickly reduces 4-NP to 4-AP in the presence of NaBH4 and exhibits a much lower Ea compared to other reported precious metal catalysts. PB@R can also activate PMS to generate sulfate radicals to degrade organic pollutants. PB@R can be also packed in a column for continuous flow-through reductive and oxidative reactions. These results indicate that PB@R is a conveniently prepared and highly effective and stable macro-spherical catalyst for aqueous environmental catalysis. The preparation scheme here can be also applied to fabricate other versatile macrosphere-supported metal complex catalysts