In newly published study, 博彩平台推荐的化学家张伟详细介绍了一种更便宜、更可持续的新型多孔材料

For a broad range of industries, 气体分离是过程和产品的重要组成部分——从用于医疗目的的空气中分离氮气和氧气，到在碳捕获过程中从其他气体中分离二氧化碳或从天然气中去除杂质.

然而，分离气体既耗能又昂贵. “For example, when separating oxygen and nitrogen, 你需要将空气冷却到非常低的温度，直到它们液化. Then, by slowly increasing the temperature, the gases will evaporate at different points, allowing one to become a gas again and separate out,” explains Wei Zhang他是博彩平台推荐(University of Colorado Boulder)的化学教授，也是该组织的主席 Department of Chemistry.

“It’s very energy intensive and costly.”

许多气体分离依赖于气体通过并分离的多孔材料. This, too, has long presented a problem, 因为这些多孔材料通常是特定于被分离的气体类型的. 试着让其他类型的气体通过它们，它们都不起作用.

However, in research published today in the journal Science, Zhang and his co-researchers 详细介绍了一种新型的多孔材料，它可以容纳和分离许多不同的气体，由普通气体制成, readily available materials. Further, 它结合了刚性和灵活性，使基于尺寸的气体分离能够在大大降低能源成本的情况下发生.

“We are trying to make technology better,” Zhang says, “and improve it in a way that’s scalable and sustainable.”

Adding flexibility

For a long time, 用于气体分离的多孔材料是刚性的，并且根据所分离的气体类型具有亲和性. 刚性允许孔隙被明确定义，并有助于指导气体分离, 但由于分子大小的不同，也限制了可以通过的气体数量.

For several years, 张和他的研究小组致力于开发一种多孔材料，这种材料在刚性多孔材料的连接节点上引入了柔韧性元素. That flexibility allows the molecular linkers to oscillate, or move back and forth at a regular speed, 改变材料中可接近的孔径，使其适应多种气体.

“We found that at room temperature, 孔隙相对最大，柔性连接件几乎不动, so most gases can get in,” Zhang says. “当博彩平台推荐将温度从室温提高到50摄氏度左右时，, oscillation of the linker becomes larger, causing effective pore size to shrink, so larger gases can’t get in. If we keep increasing the temperature, 由于振荡增加和孔径进一步缩小，更多的气体被拒之门外. 最后，在100度时，只有最小的气体，氢气，可以通过.”

张和他的同事们开发的材料是由小有机分子组成的，与沸石最相似, a family of porous, crystalline materials mostly composed of silicon, aluminum and oxygen. “这是一种多孔材料，有很多高度有序的孔隙，”他说. “You can picture it like a honeycomb. 它的大部分是固体有机材料，这些有规则大小的孔排列并形成通道.”

研究人员使用了一种相当新型的动态共价化学，专注于硼氧键. Using a boron atom with four oxygen atoms around it, 他们利用了硼和氧之间键的可逆性, which can break and reform again and again, thus enabling self-correcting, 防错误行为并导致结构有序框架的形成.

“We wanted to build something with tunability, with responsiveness, with adaptability, 博彩平台推荐认为硼氧键可能是一个很好的组成部分，可以整合到博彩平台推荐正在开发的框架中, because of its reversibility and flexibility,” Zhang says.

Sustainable solutions

Developing this new porous material did take time, Zhang says: “Making the material is easy and simple. The difficulty was at the very beginning, 当博彩平台推荐第一次获得这种材料，需要理解或阐明它的结构——键是如何形成的, how angles form within this material, is it two-dimensional or three-dimensional. We had some challenges because the data looked promising; we just didn’t know how to explain it. It showed certain peaks (x-ray diffraction), 但博彩平台推荐无法立即弄清楚这些峰对应的是哪种结构."

So, he and his research colleagues took a step back, 在科学研究过程中，哪些是重要但很少被讨论的部分. 他们专注于小分子模型系统，其中包含与他们材料中相同的反应位点，以了解分子构建块如何在固态中包装, and that helped explain the data.

张补充说，他和他的合作研究人员在开发这种材料时考虑了可扩展性, 因为其潜在的工业用途将需要大量, “and we believe this method is highly scalable. 这些构建模块是市售的，而且不贵, so it could be adopted by industry when the time is right.”

他们已经为这种材料申请了专利，并正在继续研究其他积木材料，以了解这种方法的基板范围. 张还说，他看到了与工程研究人员合作，将这种材料整合到基于膜的应用中的潜力.

“Membrane separations generally require much less energy, so in the long term they could be more sustainable solutions,” Zhang says. “博彩平台推荐的目标是改进技术，以可持续的方式满足行业需求.”

Researchers Yiming Hu, Bratin Sengupta, Hai Long, Lacey J. Wayment, Richard Ciora, Yinghua Jin, Jingyi Wu, Zepeng Lei, Kaleb Friedman, Hongxuan Chen and Miao Yu also contributed to this study.

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