Porous carbon membranes were favorably fabricated through the pyrolysis of polyacrylonitrile (PAN) precursors

which were prepared with a template-free technique-thermally induced phase separation. These carbon membranes possess hierarchical pores

including cellular macropores across the whole membranes and much small pores in the matrix as well as on the pore walls. Nitrogen adsorption indicates micropores (1.47 and 1.84 nm) and mesopores (2.21 nm) exist inside the carbon membranes

resulting in their specific surface area as large as 1062 m2/g. The carbon membranes were used to adsorb organic dyes (methyl orange

Congo red

and rhodamine B) from aqueous solutions based on their advantages of hierarchical pore structures and large specific surface area. It is particularly noteworthy that the membranes present a selective adsorption towards methyl orange

whose molecular size (1.2 nm) is smaller than those of Congo red (2.3 nm) and rhodamine B (1.8 nm). This attractive result can be attributed to the steric structure matching between the molecular size and the pore size

rather than electrostatic attraction. Furthermore

the used carbon membranes can be easily regenerated by hydrochloric acid

and their recovery adsorption ratio maintains above 90% even in the third cycle. This work may provide a new route for carbon-based adsorbents with hierarchical pores via a template-free approach

which could be promisingly applied to selectively remove dye contaminants in aqueous effluents.