{"title":"Investigation of the Defect Cu<sup>2+</sup> Centers in the Paddle Wheel MOF: Defective Structures, EPR Spectra, and H<sub>2</sub>O Adsorption.","authors":"Chang-Chun Ding, Yong-Qiang Li, Yu-Jie Sun, Wei Jin, Tong Liu, Jun-Shan Hu","doi":"10.1021/acs.inorgchem.4c04694","DOIUrl":null,"url":null,"abstract":"<p><p>Due to the different Cu<sup>2+</sup> centers, the <sub>∞</sub><sup>3</sup>[Cu<sub>2</sub><sup>I</sup>Cu<sub>2</sub><sup>II</sup>(H<sub>2</sub>O)<sub>2</sub>L<sub>2</sub>Cl<sub>2</sub>] MOF has been widely studied using electron paramagnetic resonance (EPR) spectra, particularly regarding its capacity for gas molecule adsorption. In the present work, based on the occupation sites of Cu<sup>2+</sup> in <sub>∞</sub><sup>3</sup>[Cu<sub>2</sub><sup>I</sup>Cu<sub>2</sub><sup>II</sup>(H<sub>2</sub>O)<sub>2</sub>L<sub>2</sub>Cl<sub>2</sub>], three corresponding fragments, dimer [CuO<sub>5</sub>]-[CuO<sub>5</sub>] (C<sub>0</sub>), defective [CuO<sub>5</sub>] (C<sub>1</sub>), and [CuN<sub>4</sub>] (C<sub>2</sub>), are established to investigate the two different EPR signals (S<sub>a</sub> and S<sub>b</sub>) and the local environment of Cu<sup>2+</sup>. By applying the order perturbation formulas of the spin-Hamiltonian parameters, C<sub>0</sub> and C<sub>2</sub> can be excluded because of the EPR silence of the antiferromagnetically coupled Cu<sup>2+</sup> pair at low (7 K) temperatures and the silent signal of Cu<sup>1+</sup>. Thus, two mononuclear Cu<sup>2+</sup> ion defect species (C<sub>1</sub><sup>a</sup> and C<sub>1</sub><sup>b</sup>) in <sub>∞</sub><sup>3</sup>[Cu<sub>2</sub><sup>I</sup>Cu<sub>2</sub><sup>II</sup>(H<sub>2</sub>O)<sub>2</sub>L<sub>2</sub>Cl<sub>2</sub>] can account for signals S<sub>a</sub> and S<sub>b</sub>, indicating two distinct surrounding environments of Cu<sup>2+</sup>. When the results from the density functional theory calculations are combined, the defective copper paddle wheel units are superior to the pristine ones in the adsorption of H<sub>2</sub>O, which is beneficial to the electrochemical hydrogen evolution reaction (HER) and oxygen evolution reactions (OER). Therefore, the reliability of the perturbation method to investigate the EPR spectra and the adsorption behavior of MOFs is powerfully demonstrated, which can reduce the time consumed by current first-principles calculations.</p>","PeriodicalId":40,"journal":{"name":"Inorganic Chemistry","volume":" ","pages":""},"PeriodicalIF":4.3000,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Inorganic Chemistry","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1021/acs.inorgchem.4c04694","RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CHEMISTRY, INORGANIC & NUCLEAR","Score":null,"Total":0}
引用次数: 0
Abstract
Due to the different Cu2+ centers, the ∞3[Cu2ICu2II(H2O)2L2Cl2] MOF has been widely studied using electron paramagnetic resonance (EPR) spectra, particularly regarding its capacity for gas molecule adsorption. In the present work, based on the occupation sites of Cu2+ in ∞3[Cu2ICu2II(H2O)2L2Cl2], three corresponding fragments, dimer [CuO5]-[CuO5] (C0), defective [CuO5] (C1), and [CuN4] (C2), are established to investigate the two different EPR signals (Sa and Sb) and the local environment of Cu2+. By applying the order perturbation formulas of the spin-Hamiltonian parameters, C0 and C2 can be excluded because of the EPR silence of the antiferromagnetically coupled Cu2+ pair at low (7 K) temperatures and the silent signal of Cu1+. Thus, two mononuclear Cu2+ ion defect species (C1a and C1b) in ∞3[Cu2ICu2II(H2O)2L2Cl2] can account for signals Sa and Sb, indicating two distinct surrounding environments of Cu2+. When the results from the density functional theory calculations are combined, the defective copper paddle wheel units are superior to the pristine ones in the adsorption of H2O, which is beneficial to the electrochemical hydrogen evolution reaction (HER) and oxygen evolution reactions (OER). Therefore, the reliability of the perturbation method to investigate the EPR spectra and the adsorption behavior of MOFs is powerfully demonstrated, which can reduce the time consumed by current first-principles calculations.
期刊介绍:
Inorganic Chemistry publishes fundamental studies in all phases of inorganic chemistry. Coverage includes experimental and theoretical reports on quantitative studies of structure and thermodynamics, kinetics, mechanisms of inorganic reactions, bioinorganic chemistry, and relevant aspects of organometallic chemistry, solid-state phenomena, and chemical bonding theory. Emphasis is placed on the synthesis, structure, thermodynamics, reactivity, spectroscopy, and bonding properties of significant new and known compounds.