Methane and carbon dioxide adsorption on al-based and Zr-BASED Mofs: effects of amino-functionalization

Abstract

For natural gas storage, adsorbed natural gas (ANG) technology has attracted great attention. There is a wide range of porous materials for ANG, but the most promising porous adsorbents for natural gas are metal organic frameworks (MOFs). This study examined adsorption of carbon dioxide and methane gases on aluminium (Al) based MOFs and zirconium (Zr) based MOFs including MIL-53(Al), MIL-53(Al)-NH₂, UiO-66, UiO-66-NH₂ 25%, UiO-66-NH₂ 50%, UiO-66-NH₂ 75%, and UiO-66-NH₂. Experiments were carried out in a static system at 33°C and pressures up to 100 psi. Characterization and structural analysis of the adsorbents were investigated by Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), scanning electron microscopy (SEM), and N₂ adsorption/ desorption. The effects of amino functionalization on MIL-53(Al) and UiO-66 were discussed. The results showed that increasing the pressure led to the increase in methane and carbon dioxide adsorption. Moreover, the addition of amino functional group decreased the surface area and micropore volume but did not affect the crystalline structure. MIL-53(Al) and UiO-66-NH₂ displayed similar methane and carbon dioxide uptake, which was higher than the others. It seems that the high surface area and the effect of amino group on UiO-66-NH₂ contributed to the high methane and carbon dioxide adsorption. Furthermore, the carbon dioxide uptake was higher than the methane uptake, approximately two times due to its electrophile, which resulted in preferential adsorption toward carbon dioxide.