Improvement of the Proton Conduction of Copper(II)-Mesoxalate Metal-Organic Frameworks by Strategic Selection of the Counterions

Beatriz Gil-Hernández; Simon Millan; Irina Gruber; Miguel Quirós; David Marrero-López; Christoph Janiak; Joaquín Sanchiz

doi:10.1021/acs.inorgchem.2c01241

Improvement of the Proton Conduction of Copper(II)-Mesoxalate Metal-Organic Frameworks by Strategic Selection of the Counterions

Inorg Chem. 2022 Aug 1;61(30):11651-11666. doi: 10.1021/acs.inorgchem.2c01241. Epub 2022 Jul 15.

Authors

Beatriz Gil-Hernández^{1

2}, Simon Millan³, Irina Gruber³, Miguel Quirós⁴, David Marrero-López⁵, Christoph Janiak³, Joaquín Sanchiz^{1

2}

Affiliations

¹ Departamento de Química, Facultad de Ciencias, Sección Química, Universidad de La Laguna, La Laguna 38206, Tenerife, Spain.
² Institute of Materials and Nanotechnology, Universidad de La Laguna, P.O. Box 456, La Laguna E-38200, Tenerife, Spain.
³ Institut für Anorganische Chemie und Strukturchemie, Heinrich-Heine Universität Düsseldorf, 40204 Düsseldorf, Germany.
⁴ Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain.
⁵ Departamento de Física Aplicada I, Universidad de Málaga, Campus Teatinos s/n, 29071 Málaga, Spain.

Abstract

Three copper(II)/mesoxalate-based MOFs with formulas (H₃O)[Cu₉(Hmesox)₆(H₂O)₆Cl]·8H₂O (1), (NH₂Me₂)_0.4(H₃O)_0.6[Cu₉(Hmesox)₆(H₂O)₆Cl]·8H₂O (2), and (enH₂)_0.25(enH)_1.5[Cu₆(Hmesox)₃(mesox)(H₂O)₆Cl_0.5]Cl_0.5·5.25H₂O (3) were synthesized (H₄mesox = mesoxalic acid = 2,2-dihydroxypropanedioic acid, en = ethylenediamine). Essentially, all of the compounds display the same anionic network with a different arrangement of the cations, which have a remarkable effect on the proton conduction of the materials, ranging from 1.16 × 10^-4 S cm^-1 for 1 to 1.87 × 10^-3 S cm^-1 for 3 (at 80 °C and 95% RH). These compounds also display antiferromagnetic coupling among the copper(II) ions through both the carboxylate and alkoxido bridges. The values of the principal magnetic coupling constants were calculated by density functional theory (DFT), leading to congruent values that confirm the predominant antiferromagnetic nature of the interactions.