Tuning the Redox Activity of Metal-Organic Frameworks for Enhanced, Selective O2 Binding: Design Rules and Ambient Temperature O2 Chemisorption in a Cobalt-Triazolate Framework
Tuning the Redox Activity of Metal-Organic Frameworks for Enhanced, Selective O2 Binding: Design Rules and Ambient Temperature O2 Chemisorption in a Cobalt-Triazolate Framework
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DOI：
10.1021/jacs.9b12401
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发表时间：
2020-03-04
影响因子：
15
通讯作者：
Snurr, Randall Q.
中科院分区：
文献类型：
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作者：
Rosen, Andrew S.;Mian, M. Rasel;Snurr, Randall Q.
具有配位不饱和金属中心的金属有机骨架(MOF)由于其可调节的官能度和选择性结合小分子的能力而成为吸引人的吸附材料。通过基于周期密度泛函理论的计算筛选方法，我们研究了O-2和N-2在几个MOF族配位不饱和金属中心上的吸附。确定了可用于改变金属中心的氧化还原活性的各种设计手柄，包括改变连接体的官能化(用硫化给体取代氧化给体)、桥联配体的阴离子交换(考虑Mu-Br-、Mu-Cl-、Mu-F-或Mu-OH-基团)，以及改变金属的形式氧化状态。因此，我们证明了在涉及O-2的强和/或选择性结合的应用中，可以调节MOF的开放金属位上的O-2亲和力。与O-2吸附相比，在MOF数据集中，N-2在开放金属中心的吸附被预测为相对较弱，除了含有综合难以捉摸的V2+开放金属中心的MOF。作为筛选研究的一个例子，我们预测用M2Cl2(BBTA)(H(2)BBTA=1H，SH-苯并(1，2-d：4，5-d‘)联三唑)的Mu-Cl-配体交换M2Cl2(BBTA)(H(2)BBTA=1H，SH-苯并(1，2-d：4，5-d’)联三唑)的Mu-Cl-将显著增强O-2在金属开环上的吸附强度，而不会相应地增加N-2亲和力。Co2Cl2(BBTA)和Co2(OH)(2)(BBTA)的实验研究证实，前者对N-2和O-2的物理吸附很弱，而后者能够在室温下以高选择性的方式化学吸附O-2。O-2的化学吸附行为归因于Mu-OH-配体更强的给电子特性以及Mu-OH-桥联配体与还原的O-2吸附物之间存在氢键相互作用。
Metal-organic frameworks (MOFs) with coordinatively unsaturated metal sites are appealing as adsorbent materials due to their tunable functionality and ability to selectively bind small molecules. Through the use of computational screening methods based on periodic density functional theory, we investigate O-2 and N-2 adsorption at the coordinatively unsaturated metal sites of several MOF families. A variety of design handles are identified that can be used to modify the redox activity of the metal centers, including changing the functionalization of the linkers (replacing oxido donors with sulfido donors), anion exchange of bridging ligands (considering mu-Br-, mu-Cl-, mu-F-, or mu-OH- groups), and altering the formal oxidation state of the metal. As a result, we show that it is possible to tune the O-2 affinity at the open metal sites of MOFs for applications involving the strong and/or selective binding of O-2. In contrast with O-2 adsorption, N-2 adsorption at open metal sites is predicted to be relatively weak across the MOF dataset, with the exception of MOFs containing synthetically elusive V2+ open metal sites. As one example from the screening study, we predicted that exchanging the mu-Cl- ligands of M2Cl2(BBTA) (H(2)BBTA = 1H,SH-benzo(1,2-d:4,5-d')bistriazole) with mu-OH- groups would significantly enhance the strength of O-2 adsorption at the open metal sites without a corresponding increase in the N-2 affinity. Experimental investigation of Co2Cl2(BBTA) and Co-2(OH)(2)(BBTA) confirms that the former exhibits weak physisorption of both N-2 and O-2, whereas the latter is capable of chemisorbing O-2 at room temperature in a highly selective manner. The O-2 chemisorption behavior is attributed to the greater electron-donating character of the mu-OH- ligands and the presence of H-bonding interactions between the mu-OH- bridging ligands and the reduced O-2 adsorbate.