Cheng Hongtao, Wang Qian, Meng Liuli, Sheng Pan, Zhang Zonghui, Ding Min, Gao Yajun, Bai Junfeng
Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi'an 710062, P. R. China.
State Key Laboratory of Coordination Chemistry, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing 210093, P. R. China.
ACS Appl Mater Interfaces. 2021 Sep 1;13(34):40713-40723. doi: 10.1021/acsami.1c11971. Epub 2021 Aug 18.
Due to the ultralow amounts of CH and CH gases, to design and synthesize water-stable MOFs that are promising for real-world efficient pipeline natural gas (NG) upgrading by the recovery of individual CH and CH gases is still a great challenge. Here, a N/O/F heteroatom-rich and rooflike [Cu(II)Cu(I)(COO)(tetrazolyl)] cluster-based ultra-microporous -MOF (SNNU-Bai68) was afforded as a multiple heteroatom-rich and curved-surface-shaped cluster-based ultra-microporous MOF and the first porous MOF based upon such rooflike [Cu(II)Cu(I)(tetrazolyl)] cluster. In SNNU-Bai68, the rooflike cluster was further assembled into a 1D chain secondary building block (SBB), which led to a high density of accessible potential adsorptive sites. Very interestingly, it exhibited the most promising balance of high gas adsorption uptakes at 0.01, 0.03, and 0.05 bar, high CH/CH, CH/CH, and CH/CH adsorption selectivities, moderate adsorption enthalpies, and high water and chemical stability for pipeline natural gas upgrading by the recovery of individual CH and CH gases, which was further confirmed by the breakthrough experiments of the gas mixtures with/without 74% RH. Furthermore, the SC-XRD and GCMC studies revealed that the successful separation of CH, CH, and CH gases in SNNU-Bai68 is due to different synergistic effects of H-bonds between the frameworks at three adsorptive sites around each rooflike cluster and those different gas molecules, which were initially described systematically by the number of H atoms from the gas molecules, the total number of H-bonds within the synergistic H-bonds, and the binding energy of the framework at an adsorption site toward the gas molecules. In addition, this work may provide a method for the construction of a multiple heteroatom-rich and curved-surface-shaped cluster-based ultra-microporous MOF as a novel approach to build MOFs with polar pore surfaces, suitable pore sizes, and unique pore shapes to maximize the synergistic H-bonds between the framework and guests.
由于CH和CH气体的含量极低，设计并合成对通过回收单个CH和CH气体实现实际高效管道天然气（NG）升级具有前景的水稳定金属有机框架（MOF）仍然是一项巨大挑战。在此，一种富含N/O/F杂原子且呈屋顶状的基于[Cu(II)Cu(I)(COO)(四唑基)]簇的超微孔-MOF（SNNU-Bai68）被制备出来，它是一种富含多种杂原子且具有曲面形状的基于簇的超微孔MOF，也是首个基于此类屋顶状[Cu(II)Cu(I)(四唑基)]簇的多孔MOF。在SNNU-Bai68中，屋顶状簇进一步组装成一维链状二级构筑单元（SBB），这导致了高密度的可及潜在吸附位点。非常有趣的是，它在0.01、0.03和0.05 bar下展现出了最具前景的高气体吸附量、高CH/CH、CH/CH和CH/CH吸附选择性、适中的吸附焓以及通过回收单个CH和CH气体实现管道天然气升级的高水稳定性和化学稳定性的平衡，这在含/不含74%相对湿度的气体混合物的突破实验中得到了进一步证实。此外，单晶X射线衍射（SC-XRD）和巨正则蒙特卡罗（GCMC）研究表明，SNNU-Bai68中CH、CH和CH气体的成功分离是由于每个屋顶状簇周围三个吸附位点处框架与不同气体分子之间氢键的不同协同效应，这些效应最初通过气体分子中的H原子数量、协同氢键内氢键的总数以及吸附位点处框架对气体分子的结合能进行了系统描述。此外，这项工作可能为构建富含多种杂原子且具有曲面形状的基于簇的超微孔MOF提供一种方法，作为构建具有极性孔表面、合适孔径和独特孔形状以最大化框架与客体之间协同氢键的MOF的新途径。
