Understanding the effect of gas molecules on the framework structures upon gas sorption in porous materials is highly desirable for the development of gas storage and separation technologies. However, this remains challenging for flexible metal–organic frameworks (MOFs) which feature “gate-opening/gate-closing” or “breathing” sorption behaviors under external stimuli. Herein, we report such a flexible Cd-MOF that exhibits “gating effect” upon CO₂ sorption. The ability of the desolvated flexible Cd-MOF to retain crystal singularity under high pressure enables the direct visualization of the reversible closed-/open-pore states before and after the structural transformation as induced by CO₂ adsorption/desorption through in situ single-crystal X-ray diffraction experiments. The binding sites of CO₂ molecules within the flexible MOF under high pressure and room temperature have also been identified via combined in situ single-crystal X-ray diffraction and powder X-ray diffraction studies, facilitating the elucidation of the states observed during gate-opening/gate-closing behaviors. Our work therefore lays a foundation to understand the high-pressure gas sorption within flexible MOFs at ambient temperature, which will help to improve the design efforts of new flexible MOFs for applications in responsive gas sorption and separation.

中文翻译：

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在高压和室温下可视化柔性有机金属框架中的结构转变和宾客结合

对于气体存储和分离技术的发展，非常需要了解气体分子在多孔材料上吸附气体后对骨架结构的影响。但是，这对于具有外部刺激下的“开门/关门”或“呼吸”吸附行为的柔性金属有机框架（MOF）仍然具有挑战性。在本文中，我们报道了这样一种灵活的Cd-MOF，它对CO _2的吸附表现出“门控效应” 。脱溶剂的柔性Cd-MOF在高压下保持晶体奇异性的能力可以直接观察结构转变前后可逆的闭孔/开孔状态，这是由原位CO ₂吸附/解吸引起的单晶X射线衍射实验。还通过结合原位单晶X射线衍射和粉末X射线衍射研究确定了柔性MOF在高压和室温下CO ₂分子的结合位点，从而有助于阐明门控期间观察到的状态。打开/关闭门的行为。因此，我们的工作为理解柔性MOF在环境温度下的高压气体吸附奠定了基础，这将有助于改善用于响应性气体吸附和分离的新型柔性MOF的设计工作。