Zeolitic-imidazole framework ZIF-8 has attracted tremendous interests for the high-resolution kinetic separation of propylene/propane mixture due to its effective aperture size in between the sizes of propylene and propane molecules. It is of great interest to fine-tune the effective aperture size of ZIF-8 either to improve its propylene/propane separation performances or to extend its use to the separation of other gas mixtures. It has been shown that substituting Zn with other metal nodes (e.g. Co) is a potential means to fine-tune the effective aperture size of ZIF-8. Here, we attempt to introduce another metal center, Cd, into ZIF-8 in a facile and scalable manner. Phase-pure Cd-ZIF-8 was successfully synthesized in methanol using a conventional solvothermal method, although it showed a narrow synthesis window. The presence of an organic base (triethylamine, TEA) was found critical not only for the facile synthesis of phase-pure Cd-ZIF-8 but also for the suppression of its phase transformation. A battery of characterizations including single-crystal X-ray structure solutions confirmed that the effective aperture size of Cd-ZIF-8 is the largest among its iso-structures (Zn-ZIF-8 and Co-ZIF-8). Finally, for the first time, mixed-metal CdZn-ZIF-8 crystals with various Cd/Zn ratios were solvothermally synthesized, demonstrating a further opportunity for varying the effective aperture sizes of ZIF-8 and its iso-structures.

沸石-咪唑骨架ZIF-8因其在丙烯和丙烷分子大小之间的有效孔径而对高分辨率的丙烯/丙烷混合物动力学分离引起了极大的兴趣。微调ZIF-8的有效孔径大小以改善其丙烯/丙烷分离性能或将其用途扩展到其他气体混合物的分离，这一点引起了极大的兴趣。已经显示用其他金属节点（例如Co）代替Zn是微调ZIF-8的有效孔径尺寸的潜在手段。在这里，我们尝试以方便且可扩展的方式将另一个金属中心Cd引入ZIF-8。尽管纯相Cd-ZIF-8的合成窗口很窄，但它已使用常规溶剂热法成功地在甲醇中合成。发现有机碱（三乙胺，TEA）的存在不仅对于轻松合成纯相Cd-ZIF-8至关重要，而且对于抑制其相变也至关重要。包括单晶X射线结构解决方案在内的一系列表征证实，Cd-ZIF-8的有效孔径是其同构结构（Zn-ZIF-8和Co-ZIF-8）中最大的。最后，首次溶剂热合成了具有各种Cd / Zn比的CdZn-ZIF-8混合金属晶体，这为改变ZIF-8的有效孔径及其同构结构提供了进一步的机会。包括单晶X射线结构解决方案在内的一系列表征证实，Cd-ZIF-8的有效孔径是其同构结构（Zn-ZIF-8和Co-ZIF-8）中最大的。最后，首次溶剂热合成了具有各种Cd / Zn比的CdZn-ZIF-8混合金属晶体，这为改变ZIF-8的有效孔径及其同构结构提供了进一步的机会。包括单晶X射线结构解决方案在内的一系列表征证实，Cd-ZIF-8的有效孔径是其同构结构（Zn-ZIF-8和Co-ZIF-8）中最大的。最后，首次溶剂热合成了具有各种Cd / Zn比的CdZn-ZIF-8混合金属晶体，这为改变ZIF-8的有效孔径及其同构结构提供了进一步的机会。