热力学证据 CO2-负荷金属-有机框架 Zn(MeIm) 2的结构变化从热容量测量
Peter F Rosen1, Matthew S Dickson1, Jason J Calvin1
1Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602, United States.
Journal of the American Chemical Society
|February 20, 2020
概括
这项研究揭示了在捕获二氧化碳 (CO2) 时二甲基酸框架 (ZIF-8) 的热容量变化. 这些测量提供了CO2诱导的ZIF-8材料内的热力学证据.
科学领域:
- 材料科学
- 热力学
- 化学学
背景情况:
- 金属有机框架 (MOF) 是多孔材料,在气体封存中具有应用.
- 一个MOF的子类 - - 氧化伊米达酸框架 (ZIF) 对于二氧化碳 (CO2) 捕获特别有前途.
- ZIF-8是一种特定的ZIF,它显示了二氧化碳封存的潜力.
研究的目的:
- 为了研究ZIF-8的低温热容量,使用不同数量的吸附CO2.
- 确定ZIF-8中二氧化碳吸附引起的结构变化的热力学证据.
- 了解二氧化碳与ZIF-8框架在分子层面上的相互作用.
主要方法:
- 对含有不同数量的CO2的ZIF-8样本进行了低温热容量测量 (每molZIF-8高达0.99molCO2).
- 在1.8K到300K的温度范围内进行测量.
- 分析的重点是识别热容量的异常,以推断结构转变和相互作用.
主要成果:
- 具有显著的二氧化碳负载 (≥0.56mol CO2/mol ZIF-8) 的样本显示出70-220K之间的广泛热容异常,表明吸附引起的结构转变.
- 这种异常部分归因于门开放过渡和二氧化碳重新排列/晶格扩张.
- 在所有带有CO2的样本中观察到70K以下的微妙异常,这表明CO2/ZIF-8相互作用导致了新的振动模式.
结论:
- 这项研究提供了ZIF-8在二氧化碳吸附过程中发生结构转变的第一个热力学证据.
- 二氧化碳吸附导致ZIF-8框架发生重大变化,包括门开放现象和格子修改.
- 这些发现有助于更好地理解MOF中的气体框架相互作用,这对于设计先进的二氧化碳捕获材料至关重要.
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