One-pot synthesis of magnetically separable ordered mesoporous carbon

Abstract

Ordered mesoporous carbon materials with magnetic frameworks have been synthesized via a “one-pot” block-copolymer self-assembly strategy associated with a direct carbonization process from resol, ferric citrate and triblock copolymer F127. The effects of iron loading on framework, pore features and magnetic properties of the resultant mesostructured maghemite/carbon composites were investigated by SAXS, WXRD, TEM, N₂ sorption, TG and magnetometer measurements. The results show that the mesoporous nanocomposites with a low γ-Fe₂O₃ content (such as 9.0 wt%) possess an ordered 2-D hexagonal (p6mm) structure, uniform mesopores (∼4.0 nm), high surface areas (up to 590 m²/g) and pore volumes (up to 0.48 cm³/g). Maghemite nanocrystals with a small particle size (∼9.3 nm) are confined in the matrix of amorphous carbon frameworks. With the increase in γ-Fe₂O₃ content, the surface area and pore volume of the nanocomposites decrease. The particle size of the γ-Fe₂O₃nanocrystals increases up to 13.1 nm. The iron oxide particles can extend from the carbon walls into mesopore channels, and hence bring a rough pore surface and gradually break down the mesoscopic regularity. The maghemite/carbon nanocomposites exhibit excellent superparamagnetic behaviors. The saturation magnetization strength can be easily adjusted from 2.5 to 12.1 emu/g by increasing the content of γ-Fe₂O₃. Further H₂O₂oxidation treatment of the magnetic nanocomposites endows plenty of oxygen-containing functional groups on the carbon surface, which improves their hydrophilic properties efficiently. The γ-Fe₂O₃ particles, embedding into the carbon matrix, show high stability during the H₂O₂oxidation process. Such modified nanocomposites with hydrophilic and magnetic framework show evidently improved adsorption properties of water and fuchsin base dye molecules in water and an easy separation procedure.