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

Two types of magnetic cobalt-carbon composites were synthesized via one-step calcination of cobalt based metal organic frameworks (MOFs), ZIF-67 and Co-3(BTC)(3).12H(2)O, 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).12H(2)O) organic linkers. Calcination of ZIF-67 produced a Co-carbon composite containing N species (Co-NCC), while Co3(BTC)(3).12H(2)O 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 m(2) g(-1), and Co-CC has less porosity of 110 m(2) 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. (C) 2016 Elsevier B.V. All rights reserved.