Luminescent metal–organic frameworks (MOFs) have garnered considerable attention in various fields. Herein, we proposed a hierarchical confinement strategy based on MOF-on-MOF to tune luminescence emission ranging from blue to red including white light in a flexible way. The easily available ZIF-8 MOF was used as a host for the confinement of two kinds of size-matching dyes (perylene and rhodamine B) to obtain a layered ZIF-8@dye@ZIF-8@dye via in situ encapsulation and seed-mediated synthesis. ZIF-8@dye@ZIF-8@dye materials with different fluorescence emission in dispersed and solid states were both obtained by tuning the initial encapsulation concentration of dye and changing the structure of the inner and outer ZIF-8@dye layers. To our delight, ZIF-8@0.125perylene@ZIF-8@25RhB with white light emission in the dispersed state was obtained; meanwhile, ZIF-8@0.125perylene + 25RhB and mechanically mixed ZIF-8@0.125perylene + ZIF-8@25RhB could not realize white light emission under the same conditions, indicating that the proposed hierarchical confinement strategy facilitated white light regulation. Similarly, the emission of ZIF-8@dye@ZIF-8@dye in the solid state has also been investigated; ZIF-8@perylene@ZIF-8@3RhB with white light emission was obtained, while white light emission could not be achieved in ZIF-8@perylene + 3RhB and ZIF-8@perylene + ZIF-8@3RhB, which further indicated the importance of the hierarchical confinement strategy based on MOF-on-MOF. The proposed hierarchical confinement strategy may also inspire the development of other functional optical MOF materials.

中文翻译：

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基于多层MOF-on-MOF的可调谐荧光发射

发光金属有机框架（MOFs）在各个领域都引起了广泛关注。在此，我们提出了一种基于 MOF-on-MOF 的分层限制策略，以灵活的方式调整从蓝色到红色（包括白光）的发光发射。以易得的 ZIF-8 MOF 作为主体，限制两种尺寸匹配的染料（苝和罗丹明 B），通过原位获得层状 ZIF-8@dye@ZIF-8@dye封装和种子介导的合成。通过调整染料的初始包封浓度和改变ZIF-8@dye内外层的结构，获得了分散态和固态不同荧光发射的ZIF-8@dye@ZIF-8@dye材料。令我们高兴的是，得到了分散状态下发射白光的ZIF-8@0.125perylene@ZIF-8@25RhB；同时，ZIF-8@0.125perylene+25RhB和机械混合的ZIF-8@0.125perylene+ZIF-8@25RhB在相同条件下不能实现白光发射，表明所提出的分级限制策略有利于白光调节。同样，还研究了固态 ZIF-8@dye@ZIF-8@dye 的发射；得到具有白光发射的ZIF-8@perylene@ZIF-8@3RhB，而在 ZIF-8@perylene + 3RhB 和 ZIF-8@perylene + ZIF-8@3RhB 中无法实现白光发射，这进一步表明了基于 MOF-on-MOF 的分级限制策略的重要性。所提出的分层限制策略也可能会激发其他功能性光学 MOF 材料的发展。