Department of Chemistry, University of California , Berkeley, California 94720, United States.
Electric Power Research Institute (EPRI) , 3420 Hillview Avenue, Palo Alto, California 94304, United States.
J Am Chem Soc. 2017 Aug 2;139(30):10526-10538. doi: 10.1021/jacs.7b05858. Epub 2017 Jul 19.
In the transition to a clean-energy future, CO separations will play a critical role in mitigating current greenhouse gas emissions and facilitating conversion to cleaner-burning and renewable fuels. New materials with high selectivities for CO adsorption, large CO removal capacities, and low regeneration energies are needed to achieve these separations efficiently at scale. Here, we present a detailed investigation of nine diamine-appended variants of the metal-organic framework Mg(dobpdc) (dobpdc = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate) that feature step-shaped CO adsorption isotherms resulting from cooperative and reversible insertion of CO into metal-amine bonds to form ammonium carbamate chains. Small modifications to the diamine structure are found to shift the threshold pressure for cooperative CO adsorption by over 4 orders of magnitude at a given temperature, and the observed trends are rationalized on the basis of crystal structures of the isostructural zinc frameworks obtained from in situ single-crystal X-ray diffraction experiments. The structure-activity relationships derived from these results can be leveraged to tailor adsorbents to the conditions of a given CO separation process. The unparalleled versatility of these materials, coupled with their high CO capacities and low projected energy costs, highlights their potential as next-generation adsorbents for a wide array of CO separations.
在向清洁能源未来的转型中，CO 分离将在减轻当前温室气体排放和促进向更清洁、可再生燃料的转化方面发挥关键作用。需要具有高 CO 吸附选择性、大 CO 去除容量和低再生能的新型材料，以在大规模上高效实现这些分离。在这里，我们详细研究了九种二胺修饰的金属-有机骨架 Mg(dobpdc)（dobpdc = 4,4'-二氧联苯-3,3'-二羧酸酯）变体，这些变体的 CO 吸附等温线呈阶跃状，这是由于 CO 协同且可逆地插入金属-胺键中形成氨基甲酸铵链所致。对二胺结构的微小修改被发现可以在给定温度下将协同 CO 吸附的阈值压力提高超过 4 个数量级，并且可以根据原位单晶 X 射线衍射实验获得的同构锌骨架的晶体结构对观察到的趋势进行合理化。从这些结果得出的结构-活性关系可以用于根据特定 CO 分离过程的条件来调整吸附剂。这些材料无与伦比的多功能性，以及它们高的 CO 容量和低的预计能源成本，突出了它们作为下一代 CO 分离广泛应用的吸附剂的潜力。
