Research Institute of Unconventional Petroleum and Renewable Energy, China University of Petroleum (East China) , Qingdao 266580, China.
Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences , Qingdao 266101, China.
ACS Appl Mater Interfaces. 2015 Nov 18;7(45):25402-12. doi: 10.1021/acsami.5b07953. Epub 2015 Nov 6.
Metal-organic frameworks (MOFs) with constricted pores can increase the adsorbate density of gas and facilitate effective CO2 separation from flue gas or natural gas due to their enhanced overlapping of potential fields of the pores. Herein, an MOF with constricted pores, which was formed by narrow channels and blocks of functional groups, was fabricated from the assembly of a methyl-functionalized ligand and Zn(II) centers (termed NPC-7-Zn). Structural analysis of the as-synthesized NPC-7-Zn reveals a series of zigzag pores with pore diameters of ∼0.7 nm, which could be favorable for CO2 traps. For reinforcing the framework stability, a solvothermal metal metathesis on the pristine MOF NPC-7-Zn was performed, and a new Cu(II) MOF (termed NPC-7-Cu) with an identical framework was produced. The influence of the reaction temperatures on the metal metathesis process was investigated. The results show that the constricted pores in NPC-7-Zn can induce kinetic issues that largely slow the metal metathesis process at room temperature. However, this kinetic issue can be solved by applying higher reaction temperatures. The modified MOF NPC-7-Cu exhibits significant improvements in framework stability and thus leads to a permanent porosity for this framework. The constricted pore structure enables enhanced potential fields for these pores, rendering this MOF with high adsorbate densities for CO2 and high adsorption selectivity for a CO2/N2 gas mixture. The adsorption kinetic studies reveal that CH4 has a faster diffusion rate constant than CO2, showing a surface diffusion controlled mechanism for CO2 and CH4 adsorption.
具有缩口孔道的金属-有机骨架（MOFs）由于其增强的孔道位势重叠，可以增加气体的吸附密度，并促进从烟道气或天然气中有效分离 CO2。在此，通过功能基团的窄通道和块的组装，制备了一种具有缩口孔道的 MOF，其由甲基功能化配体和 Zn(II)中心组成（称为 NPC-7-Zn）。对合成的 NPC-7-Zn 的结构分析揭示了一系列具有约 0.7nm 孔径的锯齿形孔道，这有利于 CO2捕获。为了增强骨架稳定性，对原始 MOF NPC-7-Zn 进行了溶剂热金属复分解反应，生成了具有相同骨架的新的 Cu(II)MOF（称为 NPC-7-Cu）。研究了反应温度对金属复分解过程的影响。结果表明，NPC-7-Zn 中的缩口孔道会引发动力学问题，在室温下大大减缓金属复分解过程。然而，通过提高反应温度可以解决这个动力学问题。改性的 MOF NPC-7-Cu 在骨架稳定性方面有显著提高，从而使该骨架具有永久的孔隙率。缩口孔结构使这些孔的位势增强，使该 MOF 对 CO2 的吸附密度更高，对 CO2/N2 混合气的吸附选择性更高。吸附动力学研究表明，CH4 的扩散速率常数比 CO2 快，表明 CO2 和 CH4 吸附的表面扩散控制机制。
