Cu-BTC and Fe-BTC metal-organic frameworks: Role of the materials structural features on their performance for volatile hydrocarbons separation

Abstract

The separation of alkanes (nC5 to nC9), propane and propylene, and aromatic (benzene, toluene and o-xylene) hydrocarbons using the metal-organic frameworks Cu-BTC and Fe-BTC as stationary phase was evaluated from inverse gas chromatography data. Both materials were found able to separate mixtures of these volatile hydrocarbons. The nature of such behavior is discussed according to the possible guest-host interactions during the molecules adsorption and retention in the column and considering the molecules size and shape and the porous framework topology. From the recorded chromatographic profiles, the retention times for the considered hydrocarbons were calculated and then used to obtain the involved differential adsorption heats and the values for the separation coefficient. Cu-BTC is a long-range ordered crystalline material while Fe-BTC shows gel-like features. Such structural differences modulate the pore accessibility and the adsorption interactions. In this contribution, the effects of these structural differences on the molecules adsorption and separation are discussed. From the recorded adsorption data, information on the pore volume, adsorption potentials and probable pore topology for Fe-BTC was obtained.