Impact of defects and charge doping on O2 binding in the metal-organic framework Fe2(bdp)3 from first principles

Fe2(bdp)3 (bdp = benzene-1,4-dipyrazolate) is a metal-organic framework with delocalized electrons along iron-pyrazolate chains whose conductivity and electronic structure are greatly affected by electron doping via alkali metals including Li, Na, and K. Its tunability makes it a candidate material for O2 separations, but outstanding questions regarding the influence of defect anions in place of the bdp ligand and regarding the localization of charge upon doping the material hinder an understanding of how O2 binding can be tuned to yield ideal O2 separations performance. We perform first principles density functional theory calculations on MxFe2(bdp)3 with M = {Li, Na, K} with and without linker defects to study structural, electronic, and magnetic changes due to charge doping and defects. We study the impact of these changes on O2 binding energies with an aim toward understanding which material properties affect O2 binding the most. Our calculations are compared with results from experimental NMR and binding enthalpy studies of the material to facilitate an understanding of O2 binding in the material upon doping and in the presence of defects.