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Effect of Modified Metal Center in Ligand for CO2 Capture in Novel Zr-Based Porphyrinic Metal–Organic Frameworks: A Computational Investigation

Xu, Wenbin, Ding, Qiuyue, Sang, Pengpeng, Xu, Jing, Shi, Zemin, Zhao, Lianming, Chi, Yuhua, Guo, Wenyue
The Journal of Physical Chemistry C 2015 v.119 no.38 pp. 21943-21951
adsorption, carbon dioxide, cobalt, coordination polymers, iron, ligands, magnesium, manganese, methane, methodology, nickel, porphyrins, zirconium
A combination of grand canonical Monte Carlo (GCMC) and density functional theory (DFT) simulations was used to investigate the effect of modified metal center in ligand for CO₂ capture in novel Zr-based porphyrinic metal–organic frameworks (PCN-224-Ms, M = Mg, Fe, Co, Ni, Mn, and Zr). The results show that the MTCPP ligands (TCPP = tetrakis(4-carboxyphenyl)porphyrin) provide more favorable adsorption sites than the inorganic Zr₆ nodes for CO₂ molecules. The modification of metal center in MTCPP ligand has a remarkable effect on the single-component adsorption of CO₂ compared to CH₄ and thus enhances the adsorption of CO₂ and the selectivity of CO₂ over CH₄. Furthermore, Coulomb interaction between adsorbate and framework plays a dominant role compared with non-Coulomb interaction in the process of adsorption and separation. Among various modified metal centers, the Zr-MTCPP is found to be the best for enhancing the adsorption and selectivity of CO₂. In addition, a small amount of water has a negative effect on the selectivity of CO₂/CH₄, and its influence follows the order PCN-224-Zr > PCN-224-Mn > PCN-224-Ni, depending on the strength of Coulomb interaction between H₂O molecules and frameworks.