Kong Xiang-Jing, He Tao, Bezrukov Andrey A, Darwish Shaza, Si Guang-Rui, Zhang Yong-Zheng, Wu Wei, Wang Yingjie, Li Xia, Kumar Naveen, Li Jian-Rong, Zaworotko Michael J
Beijing Key Laboratory for Green Catalysis and Separation and Department of Chemical Engineering, College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, PR China.
Bernal Institute and Department of Chemical Sciences, University of Limerick, Limerick V94 T9PX, Ireland.
J Am Chem Soc. 2024 Oct 7;146(41):28320-8. doi: 10.1021/jacs.4c09173.
Transformation between oxidation states is widespread in transition metal coordination chemistry and biochemistry, typically occurring in solution. However, air-induced oxidation in porous crystalline solids with retention of crystallinity is rare due to the dearth of materials with high structural stability that are inherently redox active. Herein, we report a new family of such materials, four isostructural cobalt-pyrazolate frameworks of face-centered cubic, , topology, , that are sustained by Co molecular building blocks (MBBs) and dipyrazolate ligands, . were observed to spontaneously transform from Co(II) to Co(III) MBBs in air with retention of crystallinity, marking the first such instance in metal-organic frameworks (MOFs). This transformation can also be achieved through water vapor sorption cycling, heating, or chemical oxidation. The reverse reactions were conducted by exposure of to aqueous hydrazine. exhibited high gravimetric water vapor uptakes of 0.55-0.68 g g at 30% relative humidity (RH), while in the inflection point shifted to lower RH and framework stability improved. Insight into the transformation between and was gained from single crystal X-ray diffraction and spectroscopy. Overall, the crystal engineering approach we adopted has afforded a new family of MOFs that exhibit cobalt redox chemistry in a confined space coupled with high porosity.
氧化态之间的转变在过渡金属配位化学和生物化学中广泛存在，通常发生在溶液中。然而，由于缺乏具有高结构稳定性且本身具有氧化还原活性的材料，在保持结晶度的多孔晶体固体中由空气引起的氧化很少见。在此，我们报道了一类新的此类材料，即四个面心立方拓扑结构的同构钴 - 吡唑酸盐框架，它们由钴分子构建块（MBBs）和二吡唑酸盐配体支撑。观察到 在空气中自发地从Co（II）MBBs转变为Co（III）MBBs并保持结晶度，这在金属有机框架（MOF）中尚属首例。这种转变也可以通过水蒸气吸附循环、加热或化学氧化来实现。通过将 暴露于水合肼水溶液中来进行逆反应。在30％相对湿度（RH）下， 表现出0.55 - 0.68 g g的高重量水蒸气吸收量，而在 中，拐点移至较低的RH且框架稳定性提高。通过单晶X射线衍射和 光谱对 和 之间的转变有了深入了解。总体而言，我们采用的晶体工程方法提供了一类新的MOF，它们在受限空间内展现钴氧化还原化学并具有高孔隙率。
