(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

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, N_2, 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.

REFERENCES

(1) García-Ricard, O. J.; Silva-Martínez, J. C.; Hernández-Maldonado, A. J. Systematic Evaluation of Textural Properties, Activation Temperature and Gas Uptake of Cu₂(pzdc)₂L [L = Dipyridyl-Based Ligands] Porous Coordination Pillared-Layer Networks. Dalt. Trans. 2012, 41, 8922â??8930.

(2) Riascos-Rodríguez, K.; Schroeder, A. J.; Arend, M. R.; Evans, P. G.; Hernández-Maldonado, A. J. Hysteretic Adsorption of CO2 onto a Cu₂(pzdc)₂(bpy) Porous Coordination Polymer and Concomitant Framework Distortion. Dalton Trans. 2014, 43, 10877â??10884.

(3) Chen, H.; Riascos-Rodríguez, K.; Marcano-González, M. E.; Hernández-Maldonado, A. J. Cu₂(pzdc)₂L [L=dipyridyl-Based Ligands] Porous Coordination Polymers: Hysteretic Adsorption and Diffusion Kinetics of CO₂ and CH₄. Chem. Eng. J. 2016, 283, 806â??815.

(4) Matsuda, R.; Kitaura, R.; Kubota, Y.; Kobayashi, T. C.; Takata, M.; Kitagawa, S. Incommensurate Guest Adsorption in Bellows-Shaped One-Dimensional Channels of Porous Coordination Polymers. Microporous Mesoporous Mater. 2010, 129, 296â??303.

(5) Meza-Morales, P. J.; Gomez-Gualdron, D.; Curet-Arana, M. C. Insights into the Coordination Polymer Ligand Deformation upon CO₂ Adsorption through Grand Canonical Monte Carlo Simulations. In AiChe Annual Meeting; Salt Lake City, UT, 2015.

(6) Hernández-Maldonado, A. J.; Arrieta-Pérez, R. R.; Primera-Pedrozo, J. N.; Exley, J. Structure of a Porous Cu₂(pzdc)₂(bpp) (Pzdc: Pyrazine-2,3-Dicarboxylate, Bpp: 1,3-Bis(4-Pyridyl)propane) Coordination Polymer and Flexibility upon Concomitant Hysteretic CO₂ Adsorption. Cryst. Growth Des. 2015, 15, 4123â??4131.