Enhancement of Ethane Selectivity in Ethane-Ethylene Mixtures by Perfluoro Groups in Zr-Based Metal-Organic Frameworks

abstract

A series of zirconium dicarboxylate-based metal-organic frameworks (Zr MOFs) of the UiO-66 (tetrahedral and octahedral cages) or MIL-140 (triangular channels) structure type were investigated for the separation of ethane/ethylene mixtures. The adsorption, investigated both experimentally and computationally, revealed that the size and type of pores have a more pronounced effect on the selectivity than the aromaticity of the linker. The increase in pore size when changing from benzene to naphthalene (NDC) dicarboxylate ligand makes UiO-NDC less selective (1.3-1.4) than UiO-66 (1.75-1.9) within the pressure range (100-1000 kPa), while the three-dimensional (3D) pores of the UiOs favor the adsorption of ethane due to the interactions between ethane with more spacers than in the case of the 1D channels of MIL-140s. The impact of the functionalization revealed a very interesting increase of selectivity when two perfluoro groups are present on the aromatic ring (UiO-66-2CF(3)) (value of 2.5 up to 1000 kPa). Indeed, UiO-66-2CF3 revealed a unique combination of selectivity and working capacity at high pressures. This is due to a complex adsorption mechanism involving a different distribution of the guest molecules in the different cages associated with changes in the ligand/perfluoro orientation when the pressure increases, favoring the ethane adsorption at high pressures.

keywords

TOTAL-ENERGY CALCULATIONS; ADSORPTIVE SEPARATION; MOLECULAR-DYNAMICS; FORCE-FIELD; MOFS; UIO-66(ZR); IRMOF-8; OLEFIN; CLAYS; ZIF-7

subject category

Science & Technology - Other Topics; Materials Science

authors

Pires, J; Fernandes, J; Dedecker, K; Gomes, JRB; Perez-Sanchez, G; Nouar, F; Serre, C; Pinto, ML

Groups

G6 - Virtual Materials and Artificial Intelligence

Projects

Nanoporous materials as multiple therapeutic agents (IF/00993/2012/CP0172/CT0013)

CICECO - Aveiro Institute of Materials (UID/CTM/50011/2019)

acknowledgements

The work was financed by Fundacao para a Ciencia e a Tecnologia (FCT) through project IF/00993/2012/CP0172/CT0013. This work was developed in the scope of the Projects POCI-01-0145-FEDER-007679 vertical bar UID/CTM/50011/2019 (CICECO), UID/MULTI/00612/2019 (CQB), UID/ECI/04028/2019 (CERENA), and Programa Investigador FCT, financed by national funds through the FCT/MEC and cofinanced by FEDER under the PT2020 Partnership Agreement. K.D. and C.S. also acknowledge the Investissement d'avenir Labex Patrima ANR-10-LABX-0094-01. Dr. Emmanuel Magnier (ILV, Versailles) is thanked for his assistance in the synthesis of organic linkers. Dr. Nathalie Steunou and Dr. Eddy Dumas (ILV, Versailles) are thanked for their assistance in the synthesis and characterization of some MOFs. M. Bordonhos (CERENA, IST, Univ. Lisboa) is thanked for her assistance in the measurement of propylene and propane adsorption.