Ahmed DÍAZ PÁEZ1, Nicolas KEPPELER1, Omar A. EL SEOUD1, Margarida COSTA GOMES2, Rômulo AUGUSTO ANDO1
1Instituto de Química USP, São Paulo, Brazil
2Laboratoire de Chimie, Ecole Normale Supe?rieure de Lyon & CNRS, Lyon, France
The search for effective, economical and sustainable materials to mitigate CO2 emissions through fixation (carbon capture and storage, CCS) is a priority within the scientific community. Porous liquids (PL) as nonvolatile and versatile materials, has been highlighted, as a way to improve gas adsorption capacity and allow a greater diffusion within the material. The use of gemini ionic liquids (GILs) can facilitate the synthesis of porous liquids due to the large size of the ions, that precludes their penetration in the pores of the solid matrix. Herein, two novel (GILs) based on trimethylene-1,3- and pentamethylene-1,5-bis(dimethylbenzylammonium acetate) salts were synthesized, named as C3-Gem and C5-Gem, respectively. Then, two new porous liquids were prepared by mixing rational quantity of a metal organic framework, ZIF-67, with each GIL, doubling the maximum CO2 adsorption capacity in porous liquids compared to pure GILs. In this work, the main objectives are to characterize the materials before and after CO2 adsorption by vibrational spectroscopy and determine thermodynamic parameters to understand sorption mechanisms. Figure (A) shows the CO2 sorption isotherms at 308 K for materials studied. We are currently obtaining the CO2 adsorption isotherms at five different temperatures (293-323K), to assess the relative importance of the solute-solvent interactions and of solvent free volume contributions to the dissolution process. Figure (B) shows the ATR-IR spectra of ZIF-67/C5-Gem porous liquid before and after CO2 adsorption. Significant differences were observed by infrared spectroscopy in porous liquid after CO2 adsorption. The presence of the gas was confirmed by two new bands at 2335 cm-1 and 649 cm-1, that can be attributed to the nas(CO2) and the δ(CO2) of the CO2, respectively. In the spectrum of PL + CO2, other differences are observed that must be better characterized, such as the broadening of the band at 992 cm-1 and the appearance of the band at 1260 cm-1. Our aim in this study is to characterize such differences to understand the interactions between the species and correlate them with thermodynamic properties obtained, to explain how CO2 have been solvated in the new GILs and porous liquids synthesized.
Keywords: Vibrational Spectroscopy, CO2 Adsorption, Gemini Ionic Liquids.