Department of Chemistry, University of California, Berkeley, CA, USA.
Berkeley Energy and Climate Institute, University of California, Berkeley, CA, USA.
Nat Mater. 2020 May;19(5):517-521. doi: 10.1038/s41563-019-0597-8. Epub 2020 Feb 3.
Industrial processes prominently feature π-acidic gases, and an adsorbent capable of selectively interacting with these molecules could enable important chemical separations. Biological systems use accessible, reducing metal centres to bind and activate weakly π-acidic species, such as N, through backbonding interactions, and incorporating analogous moieties into a porous material should give rise to a similar adsorption mechanism for these gaseous substrates. Here, we report a metal-organic framework featuring exposed vanadium(II) centres capable of back-donating electron density to weak π acids to successfully target π acidity for separation applications. This adsorption mechanism, together with a high concentration of available adsorption sites, results in record N capacities and selectivities for the removal of N from mixtures with CH, while further enabling olefin/paraffin separations at elevated temperatures. Ultimately, incorporating such π-basic metal centres into porous materials offers a handle for capturing and activating key molecular species within next-generation adsorbents.
工业过程中显著存在π酸性气体，而一种能够选择性地与这些分子相互作用的吸附剂，可以实现重要的化学分离。生物系统利用易得的、还原的金属中心通过反馈键合相互作用来结合和激活弱的π酸性物质，如 N，并将类似的部分纳入多孔材料中，应该会为这些气态底物的吸附提供类似的机制。在这里，我们报道了一种含有暴露的钒(II)中心的金属有机骨架，这些中心能够向后供电子密度给弱的π酸，以成功针对π酸性进行分离应用。这种吸附机制，再加上大量可用的吸附位点，使得该材料在去除混合物中 CH 中的 N 时具有创纪录的 N 容量和选择性，同时还能够在高温下实现烯烃/烷烃的分离。最终，将此类π碱性金属中心纳入多孔材料中，为捕获和激活下一代吸附剂中的关键分子物种提供了一种手段。
