Towards general network architecture design criteria for negative gas adsorption transitions in ultraporous frameworks
Towards general network architecture design criteria for negative gas adsorption transitions in ultraporous frameworks
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DOI：
10.1038/s41467-019-11565-3
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发表时间：
2019-08-12
影响因子：
16.6
通讯作者：
Kaskel, Stefan
中科院分区：
文献类型：
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作者：
Krause, Simon;Evans, Jack D.;Kaskel, Stefan
可开关金属有机框架（MOFs）已被提出用于各种与能源相关的存储和分离应用，但吸附诱导的开关转换的机理理解仍处于早期阶段。在这里，我们报告负气体吸附（NGA）的关键设计标准，压力放大材料的一个违反直觉的功能，迄今为止唯一观察到的高度多孔的框架化合物（DUT-49）。这些标准是通过分析的微观力学，孔径，互穿，吸附的物理效应，并使用先进的原位X-射线和中子衍射，NMR光谱，和量热技术平行的一系列的六个isoreticular网络的吸附孔填充机制。借助于计算模型，我们确定DUT-50作为一种新的压力放大材料，具有不同的NGA转换甲烷和氩气吸附。原位中子衍射分析的甲烷（CD 4）吸附位点在111 K的巨正则Monte Carlo模拟支持揭示了一个突然的人口最大的介孔的关键填充步骤启动结构收缩和NGA。相反，互穿导致框架硬化和比孔体积减小，这两个因素有效地抑制NGA转变。
Switchable metal-organic frameworks (MOFs) have been proposed for various energy-related storage and separation applications, but the mechanistic understanding of adsorption-induced switching transitions is still at an early stage. Here we report critical design criteria for negative gas adsorption (NGA), a counterintuitive feature of pressure amplifying materials, hitherto uniquely observed in a highly porous framework compound (DUT-49). These criteria are derived by analysing the physical effects of micromechanics, pore size, interpenetration, adsorption enthalpies, and the pore filling mechanism using advanced in situ X-ray and neutron diffraction, NMR spectroscopy, and calorimetric techniques parallelised to adsorption for a series of six isoreticular networks. Aided by computational modelling, we identify DUT-50 as a new pressure amplifying material featuring distinct NGA transitions upon methane and argon adsorption. In situ neutron diffraction analysis of the methane (CD4) adsorption sites at 111 K supported by grand canonical Monte Carlo simulations reveals a sudden population of the largest mesopore to be the critical filling step initiating structural contraction and NGA. In contrast, interpenetration leads to framework stiffening and specific pore volume reduction, both factors effectively suppressing NGA transitions.