推动 Cu3(btc)2 中甲烷高体积吸收的关键因素,Journal of the American Chemical Society

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推动 Cu3(btc)2 中甲烷高体积吸收的关键因素
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2015-08-17 , DOI: 10.1021/jacs.5b06657
Zeric Hulvey _{1,

2} , Bess Vlaisavljevich , Jarad A. Mason , Ehud Tsivion , Timothy P. Dougherty _{1,

3} , Eric D. Bloch , Martin Head-Gordon , Berend Smit ₄ , Jeffrey R. Long , Craig M. Brown _{1,

5}

Affiliation

已经进行了彻底的实验和计算研究，以阐明在金属有机骨架 Cu3(btc)2（btc(3-) = 1,3,5-苯三羧酸盐；HKUST- 1）。Cu3(btc)2 及其同构类似物 Cr3(btc)2 在几个温度下测量的甲烷吸附数据表明，当金属中心改变时，体积吸附容量几乎没有差异。两种材料获得的原位中子粉末衍射数据用于定位四个顺序填充的 CD4 吸附位点。该数据明确表明，结构中的小八面体笼周围和内部的主要吸附位点比暴露的 Cu(2+) 或 Cr(2+) 阳离子更受青睐。这些结果得到了详尽的并行计算研究的支持，并与最近使用时间分辨衍射结构包络 (TRDSE) 方法报告的结果相矛盾。此外，计算研究表明，开放金属位点的强甲烷结合主要是由于甲烷-甲烷与吸附在主要位点的相邻分子的相互作用，而不是与金属中心的电子相互作用。Cu3(btc)2 的模拟甲烷吸附等温线与实验等温线表现出极好的一致性，允许进行额外的模拟，表明对金属中心、配体的修改，甚至调整整体结合焓都不会提高甲烷的工作能力存储超过测量 Cu3(btc)2 本身的存储。计算研究表明，开放金属位点的强甲烷结合主要是由于甲烷-甲烷与吸附在主要位点的相邻分子的相互作用，而不是与金属中心的电子相互作用。Cu3(btc)2 的模拟甲烷吸附等温线与实验等温线表现出极好的一致性，允许进行额外的模拟，表明对金属中心、配体的修改，甚至调整整体结合焓都不会提高甲烷的工作能力存储超过测量 Cu3(btc)2 本身的存储。计算研究表明，开放金属位点的强甲烷结合主要是由于甲烷-甲烷与吸附在主要位点的相邻分子的相互作用，而不是与金属中心的电子相互作用。Cu3(btc)2 的模拟甲烷吸附等温线与实验等温线表现出极好的一致性，允许进行额外的模拟，表明对金属中心、配体的修改，甚至调整整体结合焓都不会提高甲烷的工作能力存储超过测量 Cu3(btc)2 本身的存储。

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Critical Factors Driving the High Volumetric Uptake of Methane in Cu3(btc)2

A thorough experimental and computational study has been carried out to elucidate the mechanistic reasons for the high volumetric uptake of methane in the metal-organic framework Cu3(btc)2 (btc(3-) = 1,3,5-benzenetricarboxylate; HKUST-1). Methane adsorption data measured at several temperatures for Cu3(btc)2, and its isostructural analogue Cr3(btc)2, show that there is little difference in volumetric adsorption capacity when the metal center is changed. In situ neutron powder diffraction data obtained for both materials were used to locate four CD4 adsorption sites that fill sequentially. This data unequivocally shows that primary adsorption sites around, and within, the small octahedral cage in the structure are favored over the exposed Cu(2+) or Cr(2+) cations. These results are supported by an exhaustive parallel computational study, and contradict results recently reported using a time-resolved diffraction structure envelope (TRDSE) method. Moreover, the computational study reveals that strong methane binding at the open metal sites is largely due to methane-methane interactions with adjacent molecules adsorbed at the primary sites instead of an electronic interaction with the metal center. Simulated methane adsorption isotherms for Cu3(btc)2 are shown to exhibit excellent agreement with experimental isotherms, allowing for additional simulations that show that modifications to the metal center, ligand, or even tuning the overall binding enthalpy would not improve the working capacity for methane storage over that measured for Cu3(btc)2 itself.

更新日期：2015-08-17

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