The Origin of the Strong Interaction Between Polar Molecules and Copper (II) Paddle-Wheels in Metal Organic Frameworks

D. Ongari, D. Tiana, S. J. Stoneburner, L. Gagliardi, and B. Smit, The Origin of the Strong Interaction Between Polar Molecules and Copper (II) Paddle-Wheels in Metal Organic Frameworks J Phys Chem C 121(28), 15135 (2017) http://dx.doi.org/10.1021/acs.jpcc.7b02302

Abstract: The copper paddle-wheel is the building unit of many metal organic frameworks. Because of the ability of the copper cations to attract polar molecules, copper paddle-wheels are promising for carbon dioxide adsorption and separation. They have therefore been studied extensively, both experimentally and computationally. In this work we investigate the copper-CO2 interaction in HKUST-1 and in two different cluster models of HKUST-1: mono-copper Cu(formate)2 and di-copper Cu2(formate)4. We show that density functional theory methods severely underestimate the interaction energy between copper paddle-wheels and CO2, even including corrections for the dispersion forces. In contrast, a multireference wave function followed by perturbation theory to second order, using the CASPT2 method, correctly describes this interaction. Restricted open shell Møller-Plesset 2 method (ROS-MP2, equivalent to (2,2) CASPT2) was also found to be adequate in describing the system and was used to develop a novel force field. Our parametrization is able to predict the experimental CO2 adsorption isotherms in HKUST-1, and it is shown to be transferable to other copper paddle-wheel systems.

© Berend Smit 2019