Interactions of water confined in a metal-organic framework as studied by a combined approach of Raman, FTIR, and IR electroabsorption spectroscopies and multivariate curve resolution analysis
Interactions of water confined in a metal-organic framework as studied by a combined approach of Raman, FTIR, and IR electroabsorption spectroscopies and multivariate curve resolution analysis
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DOI：
10.1039/d0cp02958k
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发表时间：
2020-08-28
影响因子：
3.3
通讯作者：
Shigeto, Shinsuke
中科院分区：
文献类型：
--
作者：
Hiraoka, Takayuki;Shigeto, Shinsuke
水在纳米约束下表现出明显不同于散装水的特性。这些独特的性质不仅源于水与水的相互作用，也源于水与周围环境的相互作用。在这里，我们使用了振动光谱（拉曼光谱、FTIR和IR电吸收光谱）和多元曲线解析技术的组合方法来研究水在非均相约束环境中在柱状层型金属有机框架（mof）原型内的相互作用，CPL-1 ([Cu-2(pzdc)(2)（pyz)](n)，其中pzdc = 2,3-吡嗪二羧酸盐，pyz =吡嗪）。水合CPL-1微晶体的OH拉伸拉曼光谱表明，吸附的水分子类似于氢键较弱的体水亚族。FTIR光谱的多变量曲线分辨率分析监测了cpl1的水解吸，可以准确地分配骨架的羧酸盐振动模式，与MOF的水填充和空纳米孔相关，并定量确定这些孔的数量分数。此外，在此基础上，红外电吸收测量表明，吸附在CPL-1上的水与氢键相互作用对框架振动模式的电场响应影响很小。本研究结果为阐明CPL-1中的水限制提供了坚实的基础，并证明了联合振动光谱方法在研究mof内相互作用方面的潜力。
Water in nanoconfinement shows distinct properties that are markedly different from those of bulk water. These unique properties stem not only from the water-water interaction but also from the interactions between water and the surrounding confining environment. Here we used a combined approach of vibrational spectroscopies (Raman, FTIR, and IR electroabsorption) and a multivariate curve resolution technique to study the interactions of water in a heterogeneous confining environment within a prototype of pillared layer-type metal-organic frameworks (MOFs), CPL-1 ([Cu-2(pzdc)(2)(pyz)](n), where pzdc = 2,3-pyrazinedicarboxylate, pyz = pyrazine). The OH stretching Raman spectrum of hydrated CPL-1 microcrystals revealed that the adsorbed water molecules resemble the subpopulation of bulk water whose hydrogen bond is weak. Multivariate curve resolution analysis of FTIR spectra monitoring water desorption from CPL-1 allowed for accurate assignments of the framework's carboxylate vibrational modes associated with water-filled and empty nanopores of the MOF, and for quantitative determination of the number fraction of these pores. Furthermore, building on the assignments so made, IR electroabsorption measurements showed that the hydrogen-bonding interaction with water adsorbed in CPL-1 has little impact on the response to electric fields of the framework vibrational modes. The present findings altogether provide a solid basis of elucidating water confined in CPL-1 and demonstrate the potential of the combined vibrational spectroscopic method for interrogating the interactions within MOFs.