Institute for Integrated Cell-Material Sciences, Kyoto University Institute for Advanced Study, Kyoto University , Yoshida Ushinomiya-cho, Sakyo-ku, Kyoto 606-8501, Japan.
Fukui Institute for Fundamental Chemistry, Kyoto University , Takano Nishihiraki-cho 34-4, Sakyo-ku, Kyoto 606-8103, Japan.
J Am Chem Soc. 2017 Dec 20;139(50):18313-18321. doi: 10.1021/jacs.7b10110. Epub 2017 Nov 27.
Here we report a soft porous crystal possessing hemilabile cross-links in its framework that exhibits exclusive gate opening for ethylene, enabling the discriminatory adsorption of ethylene over ethane. A Co-based porous coordination polymer (PCP) bearing vinylogous tetrathiafulvalene (VTTF) ligands, [Co(VTTF)], forms Co-S bonds as intermolecular cross-links in its framework in the evacuated closed state. The PCP recognizes ethylene via d-π complexation on the accessible metal site that displaces and cleaves the Co-S bond to "unlock" the closed structure. This ethylene-triggered unlocking event facilitates remarkable nonporous-to-porous transformations that open up accessible void space. This structural transformation follows a two-step gate-opening process. Each phase, including the intermediate structure, was successfully characterized by single-crystal X-ray diffraction analysis, which revealed an intriguing "half-open" structure suggestive of a disproportionate gate-opening phenomenon. The gate-opening mechanism was also investigated theoretically; density functional theory and Monte Carlo calculations revealed that the unique "half-open" phase corresponds to a substantially stable intermediate over the possible transformation trajectories. While ethylene opens the gate, ethane does not because it is unable to coordinate to the Co center. This feature is maintained even at pressures above 1 MPa and at a temperature of 303 K, demonstrating the potential of the "gate-locking/unlocking" mechanism that exploits the hemilabile cross-linking in soft porous crystals.
在这里，我们报告了一种具有半可逆交联键的软多孔晶体，该晶体在其框架中表现出对乙烯的独特开启，能够实现乙烯对乙烷的选择性吸附。一个含有乙烯基并四硫富瓦烯（VTTF）配体的钴基多孔配位聚合物（PCP），[Co（VTTF）]，在其框架中形成了 Co-S 键作为分子间交联键，在真空封闭状态下。PCP 通过在可及的金属位上发生 d-π 络合来识别乙烯，从而取代并切断 Co-S 键以“解锁”封闭结构。这种乙烯触发的解锁事件促进了显著的非多孔到多孔的转变，打开了可及的空隙空间。这种结构转变遵循两步门控开启过程。每个相，包括中间结构，都通过单晶 X 射线衍射分析成功地进行了表征，揭示了一个有趣的“半开”结构，暗示了一种不成比例的门控开启现象。门控开启机制也进行了理论研究；密度泛函理论和蒙特卡罗计算表明，独特的“半开”相对应于在可能的转变轨迹中具有实质性稳定中间相。当乙烯打开门时，乙烷不能，因为它不能与 Co 中心配位。即使在 1 MPa 以上的压力和 303 K 的温度下，这种特性也得以保持，这表明了利用软多孔晶体中半可逆交联键的“门控锁定/解锁”机制的潜力。
