(253aq) Structural Changes on Coordination Polymer Ligands (CPL-bpp) Induced By CO2: Theoretical Study Based on Density Functional Theory and Grand Canonical Monte Carlo Simulation

Authors: 
Meza-Morales, P., University of Puerto Rico
Curet-Arana, M., University of Puerto Rico - Mayaguez
Coordination pillared-layers (CPLs) are nanoporous materials that consist of layers formed by copper and ionic pyrazine-2,3-dicarboxylate, and they are separated by nitrogenated organic linkers. It has been previously demonstrated that CPLs could potentially be exploited for CO2 capture applications.1â??3 Some of these materials, such as CPL-2, CPL-4, and CPL-5, exhibit structural changes triggered by CO2 adsorption, which results in an enhancement of the pore volume leading to an increment of CO2 adsorption uptake.2,4,5

CPL-bpp is a member of the CPL series, which consists of layers formed by copper and ionic pyrazine-2,3-dicarboxylate that are separated by 1,3-bis(4-pyridyl)propane (bpp). This material possesses uniform pore channels, and it is a promising material for CO2 air-capture applications because it has remarkable adsorption affinity for CO2 compared to other molecules, such as O2, N2, and CH4.6

In this work, we used periodic density functional theory (DFT) calculations to elucidate the structural changes induced by CO2 on this material. Calculations were performed using PBE as exchange-correlation functional in VASP. We optimized the unit cell of CPL-bpp with various CO2 molecules in the system to quantify the effect of CO2 on the unit cell parameters. Our results indicate that CO2 induces changes in the unit cell of CPL-bpp, and the magnitude of these changes are dependent on the number of CO2 molecules in the system. Our results also demonstrate that the aromatic rings on the bpp ligands rotate with increasing number of CO2 molecules. Grand canonical Monte Carlo (GCMC) simulations were performed to obtain CO2 simulated isotherms, which were compared with experimental data available in the literature. Our results shed light into the interplay between CO2 adsorption and CPL-bpp structural changes triggered by its interaction with CO2.

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