Reduction of p-nitrophenol by magnetic Co-carbon composites derived from metal organic frameworks

• Two types of magnetic Co-carbon composites are prepared from Co-based MOFs.
• Both composites are active in catalyzing the reduction of p-nitrophenol.
• N containing Co-carbon shows better performance in catalyzing the reaction.

Two types of magnetic cobalt-carbon composites were synthesized via one-step calcination of cobalt-based metal organic frameworks (MOFs), ZIF-67 and Co3(BTC)3·12H2O, and applied as catalysts in the reduction of p-nitrophenol by NaBH4. The MOFs precursors were respectively structured by using 2-methylimidazole (ZIF-67) and 1,3,5-benzenetricarboxylic acid (Co3(BTC)3·12H2O) organic linkers. Calcination of ZIF-67 produced a Co-carbon composite containing N species (Co-NCC), while Co3(BTC)3·12H2O produced a simple Co-carbon composite (Co-CC). The prepared composites were characterized by a series of spectroscopic instruments and a surface analyzer. Raman spectra of the composites suggested carbons in both composites are present as graphitic oxide phases. Surface analyses indicated Co-NCC is highly porous with surface area of 298 m2 g−1, and Co-CC has less porosity of 110 m2 g−1. Both catalysts were active in catalyzing the reduction of p-nitrophenol to p-aminophenol, but Co-NCC exhibited much better performance to give pseudo-first-order rate constant 6.7 times greater than Co-CC, and robust reusability to complete five cycles of p-nitrophenol reduction with minimal loss of catalytic capability. The superior catalytic property of Co-NCC is attributed to the presence of N-moieties that provided additional reduction sites along with considerable porosity of the material.

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