Diffusion-Coupled Molecular Assembly: Structuring of Coordination Polymers Across Multiple Length Scales

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• 作者：Kenji Hirai ; Julien Reboul ; Nobuhiro Morone ; John E. Heuser ; Shuhei Furukawa ; Susumu Kitagawa
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：October 22, 2014
• 年：2014
• 卷：136
• 期：42
• 页码：14966-14973
• 全文大小：469K
• ISSN：1520-5126

文摘

Porous coordination polymers (PCPs) are an intriguing class of molecular-based materials because of the designability of framework scaffolds, pore sizes and pore surface functionalities. Besides the structural designability at the molecular scale, the structuring of PCPs into mesoscopic/macroscopic morphologies has attracted much attention due to the significance for the practical applications. The structuring of PCPs at the mesoscopic/macroscopic scale has been so far demonstrated by the spatial localization of coordination reactions on the surface of templates or at the phase boundaries. However, these methodologies have never been applied to the fabrication of solid-solution or multivariate metal鈥搊rganic frameworks (MOFs), in which multiple components are homogeneously mixed. Herein, we demonstrate the structuring of a box-type superstructure comprising of a solid-solution PCP by integrating a bidirectional diffusion of multiple organic ligands into molecular assembly. The parent crystals of [Zn₂(ndc)₂(bpy)]_n were placed in the DMF solution of additional organic component of H₂bdc, and the temperature was rapidly elevated up to 80 掳C (ndc = 1,4-naphthalenedicarboxylate, bpy = 4,4鈥?bipyridyl, bdc = 1,4-benzenedicarboxylate). The dissolution of the parent crystals induced the outward diffusion of components; contrariwise, the accumulation of the other organic ligand of H₂bdc induced the inward diffusion toward the surface of the parent crystals. This bidirectional diffusion of multiple components spatially localized the recrystallization at the surface of cuboid parent crystals; therefore, the nanocrystals of a solid-solution PCP ([Zn₂(bdc)_1.5(ndc)_0.5(bpy)]_n) were organized into a mesoscopic box superstructure. Furthermore, we demonstrated that the box superstructures enhanced the mass transfer kinetics for the separation of hydrocarbons.