Li Tong, Jia Xiaoxia, Chen Hui, Chang Zeyu, Li Libo, Wang Yong, Li Jinping
Shanxi Key Laboratory of Gas Energy Efficient and Clean Utilization, Taiyuan University of Technology, Taiyuan 030024, China.
College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, China.
ACS Appl Mater Interfaces. 2022 Apr 6;14(13):15830-15839. doi: 10.1021/acsami.2c01156. Epub 2022 Mar 23.
Adsorption separation technology using adsorbents is promising as an alternative to the energy-demanding cryogenic distillation of natural gas (CH/N) separation. Although a few adsorbents, such as metal-organic frameworks (MOFs), with high performance for CH/N separation, have been reported, it is still challenging to target the desired adsorbents for the actual CH/N separation under humid conditions because the adsorption capacity and selectivity of the adsorbents might be mainly dampened by water vapor. Except for the high CH uptake and CH/N selectivity, the adsorption material should simultaneously have excellent stability against moisture and relatively low-water absorption affinity. Here, we tuned the ligands and metal sites of reticular MOFs, Zn-benzene-1,4-dicarboxylic acid-1,4-diazabicyclo[2.2.2]octane (Zn-BDC-DABCO) (DMOF), affording a series of isostructural MOFs (DMOF-N, DMOF-A, DMOF-A, and DMOF-A). Because of the finely engineered pore size and introduced aromatic rings in the functional DMOF, gas sorption results reveal that the materials show improved performance with a benchmark CH uptake of 37 cm/g and a high CH/N adsorption selectivity of 7.2 for DMOF-A at 298 K and 1.0 bar. Moisture stability experiments show that DMOF-A is a robust MOF with low water vapor capacity even at ∼40% relative humidity (RH) because of the presence of more hydrophobic aromatic rings. Breakthrough experiments verify the excellent CH/N separation performances of DMOF-A under high humidity.
使用吸附剂的吸附分离技术有望成为天然气（CH₄/N₂）分离中高能耗低温蒸馏的替代方法。尽管已经报道了一些对CH₄/N₂分离具有高性能的吸附剂，如金属有机框架（MOF），但在潮湿条件下针对实际CH₄/N₂分离找到所需的吸附剂仍然具有挑战性，因为吸附剂的吸附容量和选择性可能主要受到水蒸气的抑制。除了高CH₄吸附量和CH₄/N₂选择性外，吸附材料还应同时具有优异的防潮稳定性和相对较低的吸水亲和力。在此，我们调整了网状MOF，即锌-苯-1,4-二甲酸-1,4-二氮杂双环[2.2.2]辛烷（Zn-BDC-DABCO）（DMOF）的配体和金属位点，得到了一系列同构MOF（DMOF-N、DMOF-A、DMOF-A和DMOF-A）。由于功能化DMOF中精心设计的孔径和引入的芳香环，气体吸附结果表明，这些材料表现出改进的性能，在298K和1.0巴下，DMOF-A的基准CH₄吸附量为37 cm³/g，CH₄/N₂吸附选择性高达7.2。水分稳定性实验表明，由于存在更多疏水芳香环，即使在相对湿度约40%（RH）的情况下，DMOF-A也是一种具有低水蒸气容量的稳健MOF。突破实验验证了DMOF-A在高湿度下优异的CH₄/N₂分离性能。
