Separation O2and N2from air is a very important and challenging endeavor. At present, separation processes based on porous adsorbentshave become attractivebecause they are low-energy consumption and low-cost. Among air separation adsorbents, O2-selective adsorbentshave unique advantageespecially in pure N2production.However, it is still difficult to develop an O2-selective adsorbent that has good selectivity, regenerability and stability at ambient temperature.
Recently, a research group led by Prof. XU Yunpeng and Prof. LIU Zhongmin from the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences found that the O2/N2adsorption selectivity can be reversed by directly decorating the Ce metal ion sites of a traditional Y zeolite with imidazole molecules, which results in a novel O2adsorbent.
Schematic illustration of the adsorption process on CeY and imidazole-decorated sample and the results of in situ XPS and theoretical calculations (Image by LIUHanbang)
The researchers prepared three imidazole-decorated samples and the results of static physical adsorption indicated that compared with CeY, decorated samples all had higher O2uptakes than that of N2, and the IAST O2/N2selectivity increased as the size of the imidazole molecules increased.Based on the results of in situ XPS and DFT theoreticalcalculations, they revealed the O2-selective adsorption mechanism of imidazole-decorated samples: the imidazole modification can change the electronic state of the Ce in the Y zeolite and increase its affinity for O2.They have unique electron transfer interactions with O2,and more electrons are transferred to O2.What's more,dsorption-desorption cycleexperiments showed that after 10 adsorption-desorption cycles, the O2adsorption capacity of the decorated samples werewell maintained.In addition,breakthrough experiments indicated that thesenovel O2adsorbents alsohadoutstanding dynamic separation ability at ambient temperature.The strategy of decorating the metal sites of zeolite with organic molecules is expected to lead to the development of other efficient adsorbents.
This work, published inMaterials Horizons, was supported by the National Natural Science Foundation of China (Grant No.21802136) and the Talent Program for Revitalization of Liaoning Province (XLYC1905017). (Text/Picture LIUHanbangand XU Yunpeng)
Directly decorated CeY zeolite for O2-selective adsorption in O2/N2 separation at ambient temperature. Hanbang Liu, Danhua Yuan, Liping Yang, Jiacheng Xing, Shu Zeng, Shutao Xu, Yunpeng Xu*,Zhongmin Liu,Materials Horizons, 9(2):688-693, 2021.
