Reversible Structural Transformation and Catalytic Potential of Lanthanide-Azobenzenetetracarboxylates

Abstract

Inspired by the catalytic potential of lanthanide coordination polymers of 3,3′,5,5′-azobenzenetetracarboxylic acid (H4abtc), two new isostructural [Ln2 III(Habtc)2(DMSO)4]·DMSO·H2O (LnIII = SmIII (I), EuIII = (II), DMSO = dimethyl sulfoxide) were synthesized and characterized. Their single-crystal structures were elucidated and described. Structural transformations of II in the solid state prompted by ligand substitution and thermal treatment were studied, from which genuine reversible transformation of II to [EuIII(Habtc)­(H2O)4]·3H2O (II′) and [EuIII(Habtc)­(H2O)2]·2H2O (II″) was revealed. This illustrates the rare case of reversible transformation in lanthanide coordination polymers. The transformation between II′ and II″ was also investigated. Structural transformations among these frameworks are discussed with regard to the coordination environment of EuIII, coordination modes of Habtc3–, and similarities and disparities in framework architecture and registration. In addition, the catalytic performance of II with and without the prior activation in CO2 cycloaddition reaction with epichlorohydrin was studied in comparison with II′ and II″. The excellent performance of II disregarding the activation process has been demonstrated with the maximum turnover number and turnover frequency of 7682 and 1921 h–1, respectively, for the activated II and 7142 and 1786 h–1, respectively, for the nonactivated II. The maintenance of the catalytic efficiency over 10 cycles of the catalysis and the regeneration process is illustrated and discussed with respect to structural transformation.

Analysis of Radioactive Iodine Trapping Mechanism by Zinc-Based Metal–Organic Frameworks with Various N-Containing Carboxylate Ligands

“…Zn-MOF-1 exhibits distinct crystal characteristic diffraction peaks at 2θ = 6.7°, 9.98°, 11.4°, 13.16°, 14.26°, 19.1°, and 24.5°, corresponding to the (002), (20−2), ( 110), ( 111), ( 202), (402), and (114) crystal planes. 49,50 Similarly, Zn-MOF-2 shows prominent crystal characteristic diffraction peaks at 2θ = 6.7°, 10.3°, 16.5°, and 18.8°, corresponding to the (200), ( 220), (420), and (440) crystal planes. 51 Both Zn-MOF-1 and Zn-MOF-2 were immersed in an acidic solution with pH 5 and an alkaline solution with pH 9 for 14 h and then conducted XRD analysis (Figure S2…”

Crystal structure and characterization of a new lanthanide coordination polymer, [Pr2(pydc)(phth)2(H2O)3]·H2O

“…Lanthanide coordination polymers (LnCPs) have attracted widespread interest because of their unique properties and wide range of potential applications, such as in luminescent temperature sensing (Rocha et al, 2016), catalysis (Sinchow et al, 2022), gas detection (Thammakan et al, 2023) and drug delivery (Wei et al, 2020). However, the high coordination numbers of the trivalent lanthanides (Ln III ) and the versatility in their coordination geometries complicates the control of intermolecular interactions and the prediction of coordination polymer frameworks.…”

Enhanced Catalytic Activity of a Copper(II) Metal–Organic Framework Constructed via Semireversible Single-Crystal-to-Single-Crystal Dehydration

“…MOF-based catalysts rely not only on the open metal sites and permanent porosity of the framework but also on other properties such as reversible structural transformation (or reproducibility) that ideally occurs in the single-crystal-to-single-crystal (SCSC) fashion. Most SCSC transitions are triggered by temperature, light, and removal of guest molecules, especially solvents, which often lead to catastrophic structural collapse of the host matrix. , However, the SCSC transformation of MOFs remains a challenge, owing to the difficulty of cleaving and establishing chemical bonds in more than one direction in the solid state. Many MOFs lose their crystallinity during the transition process.…”