Insights into dual-functional modification for water stability enhancement of mesoporous zirconium metal–organic frameworks
Insights into dual-functional modification for water stability enhancement of mesoporous zirconium metal–organic frameworks
复制标题
介孔金属锆-有机框架双功能改性增强水稳定性的见解
DOI：
10.1039/d2ta03851j
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发表时间：
2022
影响因子：
11.9
通讯作者：
Hupp, Joseph T.
中科院分区：
文献类型：
--
作者：
Liu, Jian;Anderson, Ryther;Schmalbach, Kevin M.;Sheridan, Thomas R.;Wang, Zhao;Schweitzer, Neil M.;Stein, Andreas;Mara, Nathan A.;Gomez-Gualdron, Diego;Hupp, Joseph T.
金属有机骨架(MOF)在水中的稳定性影响到它们作为化学催化剂的能力，它们在水蒸气存在下作为吸附剂的能力，以及它们作为可回收水收集器的有效性。在这里，我们考察了介孔分子筛NU-1000的四种节点修饰的变体，即甲酸盐、Acac-、TFacac-和Facac-Nu-1000的水稳定性，并与节点可达的NU-1000进行了比较。这些NU-1000突变体通过取代末端的水和羟基配体，提供了嫁接到NU-1000‘S六-锆氧基节点上的配体。含有最疏水配体的Facac-Nu-1000表现出最大的水稳定性，能够在不损失吸水能力的情况下经历至少20个吸水/解吸循环。计算研究揭示了安装的Facac配体的双重有益功能：(1)由于静电相互作用增强了骨架的机械稳定性；(2)转化和屏蔽了原本高度亲水的节点，使其免受与自由水的氢键相互作用，推测这可能导致在水排出过程中较弱的通道应力毛细管力-与NU-1000变体的自由脱水能的趋势一致。研究了水的收集和化学战剂模拟物的水解，以评估FAAC配体对NU-1000进行改性和机械稳定的功能后果。研究表明，每个吸附周期每克∼-NU-1000的捕集能力为1.1FAAC-NU-1000 L水蒸气。他们还发现，在20个吸水和释放周期后，催化MOF活性保持不变。这项研究为宽沟道MOF在除水过程中抗坍塌提供了节点配体稳定的基础。
The stability of metal–organic frameworks (MOFs) in water affects their ability to function as chemical catalysts, their capacity as adsorbents for separations in water vapor presence, and their usefulness as recyclable water harvesters. Here, we have examined water stability of four node-modified variants of the mesoporous MOF, NU-1000, namely formate-, Acac-, TFacac-, and Facac-NU-1000, comparing these with node-accessible NU-1000. These NU-1000 variants present ligands grafted to NU-1000's hexa-Zr(IV)-oxy nodes by displacing terminal aqua and hydroxo ligands. Facac-NU-1000, containing the most hydrophobic ligands, showed the greatest water stability, being able to undergo at least 20 water adsorption/desorption cycles without loss of water uptake capacity. Computational studies revealed dual salutary functions of installed Facac ligands: (1) enhancement of framework mechanical stability due to electrostatic interactions; and (2) transformation and shielding of the otherwise highly hydrophilic nodes from H-bonding interactions with free water, presumably leading to weaker channel-stressing capillary forces during water evacuation – consistent with trends in free energies of dehydration across the NU-1000 variants. Water harvesting and hydrolysis of chemical warfare agent simulants were examined to gauge the functional consequences of modification and mechanical stabilization of NU-1000 by Facac ligands. The studies revealed a harvesting capacity of ∼1.1 L of water vapor per gram of Facac-NU-1000 per sorption cycle. They also revealed retention of catalytic MOF activity following 20 water uptake and release cycles. This study provides insights into the basis for node-ligand-engendered stabilization of wide-channel MOFs against collapse during water removal.