Feng Liang, Yuan Shuai, Li Jia-Luo, Wang Kun-Yu, Day Gregory S, Zhang Peng, Wang Ying, Zhou Hong-Cai
Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, United States.
College of Chemistry, Tianjin Normal University, Tianjin, 300387, China.
ACS Cent Sci. 2018 Dec 26;4(12):1719-1726. doi: 10.1021/acscentsci.8b00722. Epub 2018 Dec 12.
Multivariate (MTV) hierarchical metal-organic frameworks (MOFs), which contain multiple regions arranged in ordered structures, show promise for applications such as gas separation, size-selective catalysis, and controlled drug delivery. However, the complexity of these hierarchical MOFs is limited by a lack of control during framework assembly. Herein, we report the controlled generation of hierarchical MOF-on-MOF structural formation under the guidance of two design principles, surface functionalization and retrosynthetic techniques for stability control. Accordingly, the tunability of spatial distributions, compositions, and crystal sizes has been achieved in these hierarchical systems. The resulting MOF-on-MOF hierarchical structures represent a unique crystalline porous material which contains a controllable distribution of functional groups and metal clusters that are associated together within a framework composite. This general synthetic approach not only expands the scope and tunability of the traditional MTV strategy to multicomponent materials, but also offers a facile route to introduce variants and sequences to sophisticated three-dimensional hierarchical and cooperative systems. As a proof of concept, the photothermal effects of a porphyrinic core-MOF are exploited to trigger the controlled guest release from a shell-MOF with high guest capacity, highlighting the integrated cooperative behaviors in multivariate hierarchical systems.
多变量（MTV）分级金属有机框架（MOF）包含以有序结构排列的多个区域，在气体分离、尺寸选择性催化和可控药物递送等应用中显示出前景。然而，这些分级MOF的复杂性受到框架组装过程中缺乏控制的限制。在此，我们报告了在表面功能化和稳定性控制的逆合成技术这两个设计原则的指导下，可控生成分级的MOF-on-MOF结构。因此，在这些分级体系中实现了空间分布、组成和晶体尺寸的可调性。所得的MOF-on-MOF分级结构代表了一种独特的晶体多孔材料，其包含在框架复合材料中相互关联的官能团和金属簇的可控分布。这种通用的合成方法不仅将传统MTV策略的范围和可调性扩展到多组分材料，还为向复杂的三维分级和协同体系引入变体和序列提供了一条简便途径。作为概念验证，利用卟啉核心-MOF的光热效应触发具有高客体容纳能力的壳-MOF的可控客体释放，突出了多变量分级体系中的综合协同行为。
