Kim Hyun-Chul, Huh Seong, Lee Do Nam, Kim Youngmee
Department of Chemistry and Protein Research Center for Bio-Industry, Hankuk University of Foreign Studies, Yongin 17035, Republic of Korea.
Ingenium College of Liberal Arts (Chemistry), Kwangwoon University, Seoul 01897, Republic of Korea.
Dalton Trans. 2018 Apr 3;47(14):4820-4826. doi: 10.1039/C7DT04134A.
Lewis basic heteroatoms orderly located inside the well-defined channels of metal-organic frameworks (MOFs) are potentially ideal active sites for selective gas sorption and catalysis. To develop functional MOFs with Lewis basic sites inside channels, a new C2h-symmetric dicarboxylate-based bridging ligand, 3,3'-(pyrazine-2,5-diyl)dibenzoic acid (3,3'-PDBA), was prepared by a Suzuki coupling reaction. Subsequently, two new Zn-MOFs containing the C2h-symmetric 3,3'-PDBA bridging ligand and two different bis(pyridyl)-based pillars, 1,2-bis(4-pyridyl)ethane (bpa) or 1,2-bis(4-pyridyl)ethylene (bpe), were prepared through a thermal reaction in N,N-dimethylformamide (DMF). The resulting two Zn-MOFs of the general formula of three-dimensional (3D) [Zn2(μ4-3,3'-PDBA)2(μ2-bpa)]3·(DMF)5(H2O)13 (1) or 3D-like 2D [Zn2(μ4-3,3'-PDBA)2(μ2-bpe)]·(H2O) (2) displayed primitive cubic pcu net and 2D sql net, respectively. Both Zn-MOFs 1 and 2 contain uncoordinated Lewis basic pyrazinyl nitrogen atoms in the frameworks. The solvent-free 1 with flexible bpa linkers only showed a potential porosity of 15.9% by PLATON analysis. Zn-MOF 1 with openly accessible Lewis basic sites exhibited selective sorption of CO2 over N2, H2, and CH4 at low temperature. The adsorption and desorption isotherms for CO2 sorption at 196 K showed phenomenal hysteretic behaviour indicative of a breathing process through an adsorbate-discriminatory gate-opening process toward CO2 at a low gas pressure.
有序位于金属有机框架（MOF）明确界定通道内的路易斯碱性杂原子，对于选择性气体吸附和催化而言，可能是理想的活性位点。为了开发通道内具有路易斯碱性位点的功能性MOF，通过铃木偶联反应制备了一种新型的基于C2h对称二羧酸酯的桥连配体3,3'-（吡嗪-2,5-二基）二苯甲酸（3,3'-PDBA）。随后，通过在N，N-二甲基甲酰胺（DMF）中进行热反应，制备了两种新型的含C2h对称3,3'-PDBA桥连配体以及两种不同的双（吡啶基）支柱（1,2-双（4-吡啶基）乙烷（bpa）或1,2-双（4-吡啶基）乙烯（bpe））的锌基MOF。所得的两种通式为三维（3D）[Zn2（μ4-3,3'-PDBA）2（μ2-bpa）]3·（DMF）5（H2O）13（1）或类3D二维[Zn2（μ4-3,3'-PDBA）2（μ2-bpe）]·（H2O）（2）的锌基MOF，分别呈现原始立方pcu网络和二维sql网络。锌基MOF 1和2在框架中均含有未配位的路易斯碱性吡嗪基氮原子。通过PLATON分析，具有柔性bpa连接体的无溶剂1仅显示出15.9%的潜在孔隙率。具有开放可及路易斯碱性位点的锌基MOF 1在低温下对CO2表现出相对于N2、H2和CH4的选择性吸附。在196K下CO2吸附的吸附和解吸等温线显示出显著的滞后行为，这表明在低气压下通过对吸附质有区分性的开门过程对CO2进行呼吸过程。
