Yang Shuai-Liang, Zhang Xiang, Wang Qing, Wu Chao, Liu Haiming, Jiang Dongmei, Lavendomme Roy, Zhang Dawei, Gao En-Qing
Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, P. R. China.
School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, P. R. China.
JACS Au. 2023 Jul 28;3(8):2183-2191. doi: 10.1021/jacsau.3c00243. eCollection 2023 Aug 28.
Confinement of discrete coordination cages within nanoporous lattices is an intriguing strategy to gain unusual properties and functions. We demonstrate here that the confinement of coordination cages within metal-organic frameworks (MOFs) allows the spin state of the cages to be regulated through multilevel host-guest interactions. In particular, the confined in situ self-assembly of an anionic FeL nanocage within the mesoporous cationic framework of MIL-101 leads to the ionic MOF with an unusual hierarchical host-guest structure. While the nanocage in solution and in the solid state has been known to be invariantly diamagnetic with low-spin Fe, FeL@MIL-101 exhibits spin-crossover (SCO) behavior in response to temperature and release/uptake of water guest within the MOF. The distinct color change concomitant with water-induced SCO enables the use of the material for highly selective colorimetric sensing of humidity. Moreover, the spin state and the SCO behavior can be modulated also by inclusion of a guest into the hydrophobic cavity of the confined cage. This is an essential demonstration of the phenomenon that the confinement within porous solids enables an SCO-inactive cage to show modulable SCO behaviors, opening perspectives for developing functional supramolecular materials through hierarchical host-guest structures.
将离散的配位笼限制在纳米多孔晶格中是一种获得异常性质和功能的有趣策略。我们在此证明，将配位笼限制在金属有机框架（MOF）中可通过多级主客体相互作用来调节笼的自旋状态。特别地，阴离子FeL纳米笼在MIL-101的介孔阳离子框架内原位自组装，形成具有异常分层主客体结构的离子型MOF。虽然已知溶液中和固态下的纳米笼具有低自旋Fe且始终呈抗磁性，但FeL@MIL-101会响应温度以及MOF内客体水分子的释放/吸收而表现出自旋交叉（SCO）行为。伴随水诱导SCO产生的明显颜色变化使得该材料可用于湿度的高选择性比色传感。此外，可以通过将客体包含在受限笼的疏水腔内来调节自旋状态和SCO行为。这是一个重要的现象证明，即多孔固体内的限制能够使一个无SCO活性的笼表现出可调节的SCO行为，为通过分层主客体结构开发功能性超分子材料开辟了前景。
