RESEARCH ON THE ADSORPTION OF O₂ IN METAL–ORGANIC FRAMEWORKS WITH OPEN MANGANESE(II) COORDINATION SITES

Abstract

Three different metal–organic frameworks (MOFs), specifically Mn2 (dobdc)(DMF)4 ( H2 dobdc=[2,5-dihydroxyterephthalic acid]; compound (1), Mn5 ( btac )4(μ3- OH )2( EtOH )2⋅ DMF⋅3EtOH⋅3H2O ( H2 btac=[benzotriaole-5-carboxylicacid]; compound (2), and Mn3 (2,6-ndc)3⋅4DMF ( H 2ndc=[2,6-naphthalenedicarbo-xylic acid]; compound (3), have been synthesized, the channels of which are lined with coordinatively unsaturated Mn II centers. The adsorption of O2 in these MOFs has been measured using a gravimetric method at different temperatures (-78°C, -5°C, and 25°C) at a pressure of 1 bar. Gas adsorption isotherms of compounds 1 and 2 at 298 K indicated that they bind O2 by chemisorption at low pressure, with capacities of 1.2 wt.% and 2.14 wt.%, respectively, for the first cycle, with reversible oxygen binding for compound 1 and partially irreversible oxidation for compound 2. However, compound 3 binds O2 by physisorption, with a capacity of just 0.21 wt.%. This difference between the three compounds stems from the different coordination environments of the respective Mn II centers, which give rise to differences in electron density. The results suggest that there must be an optimal electron density around the exposed Mn II center for partial charge transfer from this center to the bound O2 molecule; if the electron density is too high or too low, reversible chemisorption of O2 is not favored.

Mathematical modeling of gas desorption from a metal–organic supercontainer cavity filled with stored N2gas at critical limits

“…The mid-range mass and size of the molecule, as well as its inert character, allow the observations of this research to be extrapolated to other types of gasses and applications. Complementary gasses and applications that could benet from this study are carbon dioxide gas capture from industrial ues, 23 oxygen gas stabilization during storage, 24 and ethylene sequestration to prevent food spoilage. 25…”

Synthesis, structure and electrochemical behavior of a 3D crystalline copper(II) metal-organic framework

“…[1][2][3][4][5][6] A appropriate choice or design of ligands with suitable groups is the key for the construction of MOFs with desired structural features and functions. In recent years, a large number of long tridentate N-donor ligands have been employed extensively as the bridging linkers and terminal ligands in the construction of MOFs.…”