Graf Katerina I, Huang Adrian J, Meihaus Katie R, Long Jeffrey R
Institute for Decarbonization Materials, University of California, Berkeley, California 94720, United States.
Department of Chemistry, University of California, Berkeley, California 94720, United States.
J Am Chem Soc. 2024 Aug 28;146(34):23943-23954. doi: 10.1021/jacs.4c06718. Epub 2024 Aug 16.
Monomethylamine (NHCH), dimethylamine (NH(CH)), and trimethylamine (N(CH)) are important chemical feedstocks that are produced industrially as an azeotropic mixture and must be separated using an energy-intensive thermal distillation. While solid adsorbents have been proposed as alternatives to distillation for separating various industrial gas mixtures, methylamine separations remain largely unexplored in this context. Here, we investigate two isoreticular frameworks Cu(cyhdc) (cyhdc = -1,4-cyclohexanedicarboxylate) and Cu(bdc) (bdc = 1,4-benzenedicarboxylate) as prospective candidates for this challenging separation, motivated by the recent discovery that Cu(cyhdc) reversibly captures ammonia through a unique framework-to-coordination polymer phase change. Through a combination of gas adsorption and powder X-ray diffraction analyses, we find that Cu(cyhdc) and Cu(bdc) reversibly bind large quantities of mono- and dimethylamine through framework-to-coordination polymer phase change mechanisms, although both frameworks adsorb only moderate amounts of trimethylamine via physisorption. Single-crystal X-ray diffraction analysis of select mono- and dimethylamine containing phases suggests that the number of hydrogen bond donors available and the linker donor strength are key factors influencing amine uptake. Finally, investigation of the tricomponent adsorption behavior of both materials reveals that Cu(cyhdc) is selective for the capture of monomethylamine from a range of mono-, di-, and trimethylamine mixtures.
甲胺（NHCH）、二甲胺（NH(CH)）和三甲胺（N(CH)）是重要的化学原料，它们在工业上作为共沸混合物生产，必须通过耗能的热蒸馏进行分离。虽然已提出使用固体吸附剂替代蒸馏来分离各种工业气体混合物，但在此背景下甲胺的分离在很大程度上仍未得到探索。在此，我们研究了两种同网骨架结构Cu(cyhdc)（cyhdc = -1,4 - 环己烷二甲酸酯）和Cu(bdc)（bdc = 1,4 - 苯二甲酸酯），作为这种具有挑战性分离的潜在候选材料，这是受最近发现Cu(cyhdc)通过独特的骨架到配位聚合物相变可逆捕获氨的启发。通过气体吸附和粉末X射线衍射分析相结合，我们发现Cu(cyhdc)和Cu(bdc)通过骨架到配位聚合物相变机制可逆地结合大量的甲胺和二甲胺，尽管两种骨架结构仅通过物理吸附吸附适量的三甲胺。对选定的含甲胺和二甲胺相的单晶X射线衍射分析表明，可用氢键供体的数量和连接体供体强度是影响胺吸收的关键因素。最后，对两种材料的三组分吸附行为的研究表明，Cu(cyhdc)对于从一系列甲胺、二甲胺和三甲胺混合物中捕获甲胺具有选择性。
