Berdichevsky Ellan K, Downing Victoria A, Hooper Riley W, Butt Nathan W, McGrath Devon T, Donnelly Laurie J, Michaelis Vladimir K, Katz Michael J
Department of Chemistry, Memorial University of Newfoundland, 230 Elizabeth Avenue, St. John's, Newfoundland and Labrador A1C 5S7, Canada.
Department of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada.
Inorg Chem. 2022 May 23;61(20):7970-7979. doi: 10.1021/acs.inorgchem.2c00608. Epub 2022 May 6.
Separations based on molecular size (molecular sieving) are a solution for environmental remediation. We have synthesized and characterized two new metal-organic frameworks (MOFs) (; M = Zn, Cd) with ultramicropores (<0.7 nm) suitable for molecular sieving. We explore the synthesis of these MOFs and the role that the DMSO/HO/DMF solvent mixture has on the crystallization process. We further explore the crystallographic data for the DMSO and methanol solvated structures at 273 and 100 K; this not only results in high-quality structural data but also allows us to better understand the structural features at temperatures around the gas adsorption experiments. Structurally, the main difference between the two MOFs is that the central metal in the trimetallic node can be changed from Zn to Cd and that results in a sub-Å change in the size of the pore aperture, but a stark change in the gas adsorption properties. The separation selectivity of the MOF when M = Zn is infinite given the pore aperture of the MOF can accommodate CO while N and/or CH is excluded from entering the pore. Furthermore, due to the size exclusion behavior, the MOF has an adsorption selectivity of 4800:1 CO/N and 5 × 10:1 CO/CH. When M = Cd, the pore aperture of the MOF increases slightly, allowing N and CH to enter the pore, resulting in a 27.5:1 and a 10.5:1 adsorption selectivity, respectively; this is akin to UiO-66, a MOF that is not able to function as a molecular sieve for these gases. The data delineate how subtle sub-Å changes to the pore aperture of a framework can drastically affect both the adsorption selectivity and separation selectivity.
基于分子大小的分离（分子筛）是环境修复的一种解决方案。我们合成并表征了两种具有适用于分子筛的超微孔（<0.7纳米）的新型金属有机框架（MOF）（；M = Zn，Cd）。我们探索了这些MOF的合成以及二甲基亚砜/水/二甲基甲酰胺溶剂混合物在结晶过程中所起的作用。我们进一步探索了在273K和100K下二甲基亚砜和甲醇溶剂化结构的晶体学数据；这不仅产生了高质量的结构数据，还使我们能够更好地理解气体吸附实验温度附近的结构特征。在结构上，两种MOF之间的主要区别在于三金属节点中的中心金属可以从Zn变为Cd，这导致孔径大小发生亚埃级变化，但气体吸附性能发生了显著变化。当M = Zn时，由于MOF的孔径可以容纳CO，而N和/或CH被排除在孔外，因此该MOF的分离选择性是无限的。此外，由于尺寸排阻行为，该MOF对CO/N的吸附选择性为4800:1，对CO/CH的吸附选择性为5×10:1。当M = Cd时，MOF的孔径略有增加，使得N和CH能够进入孔中，分别导致吸附选择性为27.5:1和10.5:1；这类似于UiO - 66，一种不能对这些气体起到分子筛作用的MOF。这些数据描绘了框架孔径的细微亚埃级变化如何能极大地影响吸附选择性和分离选择性。
