Hierarchically porous carbon derived from metal-organic frameworks for separation of aromatic pollutants

Porous carbon is the most important and most common adsorbent for the separation and treatment of organic pollutants. Characteristics such as accessible and large surface area, physical and chemical stability, and low-cost manufacturing method are desired for any adsorbent. Herein, a hierarchically porous carbon (HPC) was prepared by pyrolysis and graphitization of crystalline metal-organic frameworks (MOF-5)for enhanced adsorption of aromatic contaminants. The material treated at high temperature (950 degrees C) possesses large surface area (1512 m(2)/g), high porosity (0.94 cm(3)/g), and hierarchically porous structures. The generated mesopores around 4 nm improve the interconnectivity of micro- and macropores to make the porous material ideal for sorption of organic pollutants such as aromatic hydrocarbons. Effects of adsorbent dose, pH, ionic strength, contact time, and initial concentration on the adsorption of p-nitrophenol (PNP, as a model) were investigated. Adsorption isotherms and kinetics suggest that the adsorption is a spontaneous and endothermic physisorption process with monolayer surface coverage. The surface sites are electron-rich due to the graphitic layer, which has high affinity toward pi electrons of the aromatic ring. The adsorption capacity of the hierarchically porous carbon (HPC) is nearly over 100% higher that of conventional activated carbon.