Enhancing the gas adsorption capacities of UiO-66 by nanographite addition

New composites have been synthesized containing nanographite (nGr) particles as platforms for the deposition of UiO-66 crystals. The samples were analyzed by X-ray diffraction, thermogravimetry, N2 adsorption and scanning electron microscopy. The addition of nGr markedly increased the porosity determined by N2 adsorption (0.5 nm ultramicropores were formed, and the volume in pores > 1.1 nm increased). This was the result of defects formation either on UiO-66 or at the nGr/UiO-66 interface. To assess the adsorptive properties and the accessibility of the pores, adsorption of H2, CO2, C2H4 and C2H6 was measured. The results have shown that not only the extent of the porosity but also the interactions with the graphite phase and the accessibility to the pores affect the amount adsorbed and the strength of adsorption. Generally, the formation of composites had a positive effect on the adsorption properties owing to an increased surface heterogeneity and porosity.