Understanding How Ligand Functionalization Influences CO2 and N2 Adsorption in a Sodalite Metal-Organic Framework

Published

February 25, 2020

Author(s)

Mehrdad Asgari, Rocio Semino, Pascal A. Schouwink, Ilia Kochetygov, Jacob D. Tarver, Olga Trukhina, Rajamani Krishna, Craig Brown, Michele Ceriotti, Wendy L. Queen

Abstract

In this work, a detailed study is conducted to understand how ligand substitution influences the CO₂ and N₂ adsorption properties of two highly crystalline sodalite MOFs known as Cu-BTT (BTT^-3= 1,3,5-benzenetristetrazolate) and Cu-BTTri (BTTri^-3 = 1,3,5-benzenetristriazole). The enthalpy of adsorption and observed adsorption capacities at a given pressure are significantly lower for Cu-BTTri compared to its isostructural counterpart, Cu-BTT. In situ x-ray and neutron diffraction, which allow visualization CO₂ and N₂ binding sites on the internal surface of Cu- BTTri, provide insight into understanding these subtle differences. As expected, slightly elongated distances between the open Cu²⁺ sites and surface bound CO₂ in Cu-BTTri can be explained by the fact that the triazole ligand is a better electron donor than the tetrazole. The more pronounced Jahn-Teller effect in Cu-BTTri leads to weaker guest binding. The results of the aforementioned structural analysis were also complemented by the prediction of the binding energies at each CO₂ and N₂ adsorption site by DFT calculations. In addition, variable temperature in situ diffraction measurements shed light on the fine structural changes of the framework and CO₂ occupancies at different adsorption sites as a function of temperature. Finally, simulated breakthrough curves obtained for both sodalite MOFs demonstrate the materials' potential performance in dry post-combustion CO₂ capture. The simulation, which considers both framework capacity and selectivity, predicts better separation performance for Cu-BTT. The information obtained in this work highlights how ligand substitution can influence adsorption properties and hence provides further insight into the materials optimization for important separations.

Citation

Chemistry of Materials

Volume

32

Issue

4

Pub Type

Journals

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Keywords

Metal Organic Frameworks, In situ diffraction, density functional theory, combined computational and experimental, CO2 adsorption

Citation

Asgari, M. , Semino, R. , Schouwink, P. , Kochetygov, I. , Tarver, J. , Trukhina, O. , Krishna, R. , Brown, C. , Ceriotti, M. and Queen, W. (2020), Understanding How Ligand Functionalization Influences CO₂ and N₂ Adsorption in a Sodalite Metal-Organic Framework, Chemistry of Materials, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=929763 (Accessed December 26, 2024)