Computational Exploration of a Metal(II) Catecholate-Functionalized UiO-66 Nanoporous Metal–Organic Framework for Effective NO_x Capture

Abstract

Metal–organic frameworks (MOFs) have attracted much attention for the effective capture of contaminants from air. Herein, density functional theory (DFT) calculations and grand canonical Monte Carlo (GCMC) simulations were combined to systematically assess the adsorption performance of the cagelike UiO-66 nanoporous MOF functionalized by metal­(II) catecholate [CatM­(II), where M­(II) = Mg­(II), Mn­(II), Fe­(II), Co­(II), Ni­(II), Cu­(II), Zn­(II), Pd­(II), and Pt­(II)] with respect to NO x potentially present at very low concentration (from the ppm to ppb levels). The adsorption modes and energetics of NO x toward metal­(II) catecholate functions were first examined systematically using cluster DFT calculations in order to determine the optimum metal­(II) for effective NO x capture. The best CatFe­(II) was further incorporated in the crystal structure of UiO-66 and force-field parameters to accurately describe the specific interactions between Fe­(II), and both NO x were derived from periodic DFT calculations and further implemented in a GCMC scheme to predict the adsorption isotherms in a whole range of gas pressure. These calculations revealed that UiO-66-CatFe­(II) exhibits steep-adsorption isotherms for both NO x , leading to excellent adsorption uptake at very low gas pressure (from 10–9–10–4 bar). This finding complements the portfolio of nanoporous materials that has so far been almost exclusively tested in operation conditions at much higher NO x concentration (>1000 ppm).

Ab Initio Screening of Divalent Cations for CH4, CO2, H2, and N2 Separations in Chabazite Zeolite

“…It is worth noting that our computed interaction energies for Ca-CHA are 16 kJ/mol higher than those reported in a previous study by Mikosch et al, who incorporated Ca cations in small clusters rather than a periodic cell, as in our case. This difference in energy may be attributed to the effect of confinement in bulk phase compared to clusters, as reported in previous studies …”

“…This difference in energy may be attributed to the effect of confinement in bulk phase compared to clusters, as reported in previous studies. 80 Dihydrogen (H 2 ) presents a special case since this molecule's adsorption can lead to dissociation (cation dependant), resulting in the formation of an acid bridging site on the zeolite structure (Si−OH−Al) and a metal hydride. In a separation process, this dissociative adsorption can complicate the material regeneration process and trigger undesired side reactions.…”

In Silico Design of Metal–Organic Frameworks Using Cooperative Binding of Two Metal Catecholates

“…13 Recently, Gopalsamy et al constructed M-CATs inside the UIO-66 structure, which was already experimentally synthesized, and performed DFT calculations for driving the force field for NO x capture. 14 In all of these cases, the interaction between the gas molecule and only a single metal-catecholate was assumed for analysis. It is conceivable that multiple metal catecholates can be present close to one another in a given MOF structure.…”

“…Postsynthetic modification (PSM) of the presynthesized MOFs can allow tuning of the physical and chemical properties by incorporating functionality into the secondary building blocks of MOF . To this end, anchoring of metal-catecholates (M-CATs) into MOFs is one of the fascinating topics in PSM, with the chemically active open metal sites present in the M-CATs that allow strong interaction with guest molecules to induce catalytic reactions , or gas capture and separation. – …”

“…Also, Chen and Snurr conducted high-throughput screening of 2736 hypothetical MOFs for room-temperature hydrogen storage . Recently, Gopalsamy et al constructed M-CATs inside the UIO-66 structure, which was already experimentally synthesized, and performed DFT calculations for driving the force field for NO x capture …”