Origin of the strong interaction between polar molecules and copper(II) paddle-wheels in metal organic frameworks

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Ongari, Daniele
Tiana, Davide
Stoneburner, Samuel J.
Gagliardi, Laura
Smit, Berend
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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: monocopper Cu(formate)2 and dicopper 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. The 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 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.
Carbon dioxide adsorption , Density functional theory methods , Interaction energies , Metal organic framework , Multireference wave functions , Parametrizations , Perturbation theory , Strong interaction , Carbon , Carbon dioxide , Copper , Density functional theory , Gas adsorption , Molecules , Organometallics , Perturbation techniques , Propellers
Ongari, D., Tiana, D., Stoneburner, S. J., Gagliardi, L. and Smit, B. (2017) 'Origin of the Strong Interaction between Polar Molecules and Copper(II) Paddle-Wheels in Metal Organic Frameworks', The Journal of Physical Chemistry C, 121(28), pp. 15135-15144.