Assessing the Role of Metal Identity on CO2 Adsorption in MOFs Containing M-OH Functional Groups
Assessing the Role of Metal Identity on CO2 Adsorption in MOFs Containing M-OH Functional Groups
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DOI：
10.1021/acs.chemmater.9b04228
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发表时间：
2020-01-14
影响因子：
8.6
通讯作者：
Wade, Casey R.
中科院分区：
文献类型：
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作者：
Bien, Caitlin E.;Liu, Qiao;Wade, Casey R.
通过后合成阳离子交换法制备了CFA-1[ZM4-ZX4(Bibta)(3)，bibta(2-)=5，5‘-联苯并三氮唑，M=Co(z=0)，Ni(z=1)，Cu(z=2.3)，X=Cl-，Br2-，CH3CO2-]的双金属化合物。随后的合成后X-/HCO3-配体交换和热激活在异质双金属金属-有机骨架(MOF)的Kuratowski类型的金属节点上产生亲核M-OH基团。虽然铜交换的MOF由于合成后的修饰而受到降解，但Co和Ni的类似物(Co-OH和Ni-OH)被证明是稳定的活化，室温等温线测量表明，在与直接空气捕集和其他微量CO2去除应用相兼容的压力下，CO_2的吸收率很高。与Co-OH和全锌MOF、Zn-OH相比，Ni-OH表现出更大的低压CO2容量和更高的等量吸附热。原位漫反射红外光谱(IR)实验表明，Co-OH和Ni-OH在簇间氢键作用下通过M-OH->；M-O2COH化学吸附机制吸附CO2。然而，CO2在Ni-OH中的吸附产生了Co-OH和Zn-OH中没有观察到的光谱特征，这可以归因于不参与簇间氢键的Ni-HCO3基团。对模型团簇进行的密度泛函理论(DFT)计算支持实验观察到的二氧化碳亲和力的趋势。
Heterobimetallic analogues of CFA-1 [Zn1+zM4-zX4(bibta)(3), bibta(2-) = 5,5'-bibenzotriazolate, M = Co (z = 0), Ni (z = 1), Cu (z = 2.3), X = Cl-, Br-, CH3CO2-] have been prepared via postsynthetic cation exchange. Subsequent postsynthetic X-/HCO3- ligand exchange followed by thermal activation generates nucleophilic M-OH groups at the Kuratowski-type metal nodes of the heterobimetallic metal-organic frameworks (MOFs). While the Cu-exchanged MOF suffered from degradation as a result of the postsynthetic modifications, the Co and Ni analogues (Co-OH and Ni-OH) proved to be stable to activation, and room-temperature isotherm measurements show steep CO2 uptake at pressures compatible with direct air capture and other trace CO2 removal applications. Ni-OH exhibits a greater low-pressure CO2 capacity and higher isosteric heat of adsorption than Co-OH and the all-Zn MOF, Zn-OH. In situ diffuse reflectance infrared (IR) spectroscopy experiments indicate that Co-OH and Ni-OH adsorb CO2 via a M-OH -> M-O2COH chemisorption mechanism aided by intercluster hydrogen-bonding interactions. However, CO2 adsorption in Ni-OH gives rise to spectroscopic features that are not observed for Co-OH and Zn-OH and can be attributed to Ni-bicarbonate groups that do not engage in intercluster hydrogen bonding. Density functional theory (DFT) calculations performed on model clusters support the experimentally observed trend in CO2 affinity.