Development of Ni_(x)/Mg_(1-x)-MOF-74 for highly efficient CO_(2)/N_(2) separation

双金属Ni_(x)/Mg_(1-x)-MOF-74材料用于高效CO_(2)/N_(2)分离

To enhance the separation selectivity of Mg-MOF-74 towards CO_(2) in a CO_(2)/N_(2) mixture,a series of Mg-MOF-74 and Ni_(x)/Mg_(1-x)-MOF-74 adsorbents were prepared by solvothermal synthesis in this paper.It was found that the adsorption capacity of Mg-MOF-74 for CO_(2) could be effectively increased by optimizing the amount of acetic acid.On this basis,the bimetal MOF-74 adsorbent was prepared by metal modification.The multi-component dynamic adsorption penetration analysis was utilized to examine the CO_(2) adsorption capacity and CO_(2)/N_(2) selectivity of the diverse adsorbent materials.The results showed that Ni0.11/Mg0.89-MOF-74 showed a CO_(2) adsorption capacity of 7.02 mmol/g under pure CO_(2) atmosphere and had a selectivity of 20.50 for CO_(2)/N_(2) under 15% CO_(2)/85%N_(2) conditions,which was 10.2% and 18.02% higher than that of Mg-MOF-74 respectively.Combining XPS,SEM and N_(2) adsorption-desorption characterization analysis,it was attributed to the effect of the more stable unsaturated metal sites Ni into the Mg-MOF-74 on the pore structure and the synergistic interaction between the two metals.Density Functional Theory(DFT)simulations revealed that the synergistic interaction between modulated the electrostatic potential strength and gradient of the material,which was more favorable for the adsorption of CO_(2) molecules with small diameters and large quadrupole moment.In addition,the Ni0.11/Mg0.89-MOF-74 showed commendable cyclic stability,underscoring its promising potential for practical applications.

为了提高Mg-MOF-74在CO_(2)/N_(2)混合气氛中对CO_(2)气体的分离选择性,本工作采用溶剂热合成法制备了系列的Mg-MOF-74和Ni_(x)/Mg_(1-x)-MOF-74吸附剂。通过优化合成过程中的乙酸添加量,有效提高了Mg-MOF-74对CO_(2)的吸附量。在此基础上,通过金属改性制备了双金属MOF-74吸附剂。采用多组分动态吸附穿透分析和计算模拟相结合的方法,考察了不同吸附材料对CO_(2)/N_(2)的选择性及其吸附亲和度。结果表明,在纯CO_(2)和15%CO_(2)/85%N_(2)(体积比)的常温气氛下,Ni_(0.11)/Mg_(0.89)-MOF-74对CO_(2)的动态吸附量和选择性分别为7.02 mmol/g和20.50,比Mg-MOF-74的吸附量和选择性提高了10.2%和18.02%。XPS、SEM和N_(2)吸附-脱附等表征分析得出这归因于更稳定的不饱和金属位Ni进入Mg-MOF-74结构后对孔隙结构以及双金属之间的协同作用。DFT模拟计算结果表明,两种金属间的协同作用调变了材料的静电势强度和梯度,这对小直径、大四极矩值的CO_(2)分子吸附更有利。此外,双金属Ni_(0.11)/Mg_(0.89)-MOF-74表现出良好的循环稳定性。