Department of Chemistry, Texas A&M University , College Station, Texas 77843-3255, United States.
Department of Materials Science and Engineering, University of Texas at Dallas , Richardson, Texas 75080, United States.
J Am Chem Soc. 2018 Feb 14;140(6):2363-2372. doi: 10.1021/jacs.7b12916. Epub 2018 Jan 30.
Sufficient pore size, appropriate stability, and hierarchical porosity are three prerequisites for open frameworks designed for drug delivery, enzyme immobilization, and catalysis involving large molecules. Herein, we report a powerful and general strategy, linker thermolysis, to construct ultrastable hierarchically porous metal-organic frameworks (HP-MOFs) with tunable pore size distribution. Linker instability, usually an undesirable trait of MOFs, was exploited to create mesopores by generating crystal defects throughout a microporous MOF crystal via thermolysis. The crystallinity and stability of HP-MOFs remain after thermolabile linkers are selectively removed from multivariate metal-organic frameworks (MTV-MOFs) through a decarboxylation process. A domain-based linker spatial distribution was found to be critical for creating hierarchical pores inside MTV-MOFs. Furthermore, linker thermolysis promotes the formation of ultrasmall metal oxide nanoparticles immobilized in an open framework that exhibits high catalytic activity for Lewis acid-catalyzed reactions. Most importantly, this work provides fresh insights into the connection between linker apportionment and vacancy distribution, which may shed light on probing the disordered linker apportionment in multivariate systems, a long-standing challenge in the study of MTV-MOFs.
足够大的孔径、适当的稳定性和分级多孔性是设计用于药物输送、酶固定化和涉及大分子的催化的开放式框架的三个前提条件。在此，我们报告了一种强大而通用的策略，即链接热解法，用于构建具有可调节孔径分布的超稳定分级多孔金属有机骨架（HP-MOFs）。链接体的不稳定性通常是 MOFs 的一个不理想的特性，通过热解在微孔 MOF 晶体中产生晶体缺陷，从而产生介孔。通过脱羧过程从多变量金属有机骨架（MTV-MOF）中选择性地去除热不稳定的链接体后，HP-MOF 的结晶度和稳定性仍然存在。发现基于域的链接体空间分布对于在 MTV-MOF 内部形成分级孔至关重要。此外，链接体热解促进了超小金属氧化物纳米粒子在开放骨架中的固定，该开放骨架在路易斯酸催化反应中表现出高催化活性。最重要的是，这项工作提供了关于链接体分配和空位分布之间联系的新见解，这可能有助于探究多变量系统中无序链接体分配，这是 MTV-MOF 研究中的一个长期挑战。
