Zhang Feifei, Shang Hua, Wang Li, Ma Lei, Li Kunjie, Zhang Yingying, Yang Jiangfeng, Li Libo, Li Jinping
Research Institute of Special Chemicals, College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan, Shanxi 030024, China.
Shanxi Guoxin Gas Energy Research Institute CO., Ltd, Taiyuan, Shanxi 030032, China.
ACS Appl Mater Interfaces. 2022 Jan 12;14(1):2146-2154. doi: 10.1021/acsami.1c22866. Epub 2021 Dec 22.
N removal is of great significance in high-purity O production and natural gas purification. Here, we present a substituent-induced electron-transfer strategy for improving N capture performance by controlling the Lewis acidity of Cr(III) metal unsaturated sites in Cr-based metal-organic frameworks. With the enhancement of the electron-withdrawing ability of the modified group on terephthalic acid (-NO > -CH), the N adsorption ability of MIL-101(Cr)-X was improved significantly. For MIL-101(Cr)-NO, the adsorption enthalpy of N at zero coverage was 30.01 kJ/mol, which was much larger than that of MIL-101(Cr)-CH (14.31 kJ/mol). infrared spectroscopy studies, Bader charges, and density functional theory calculations showed that the presence of -NO could enhance the Lewis acidity of Cr(III) metal unsaturated sites, which resulted in a strong interaction affinity for N. The adsorption isotherms indicated that MIL-101(Cr)-NO had an excellent N/O (79/21, v/v) selectivity of up to 10.8 and a good N/CH separation performance (S = 2.8, 298 K, 1 bar). Breakthrough curves showed that MIL-101(Cr)-NO had great potential for the efficient separation of N/O and N/CH.
氮的去除在高纯度氧气生产和天然气净化中具有重要意义。在此，我们提出一种取代基诱导的电子转移策略，通过控制铬基金属有机框架中Cr(III)金属不饱和位点的路易斯酸度来提高氮捕获性能。随着对苯二甲酸上修饰基团吸电子能力的增强（-NO > -CH），MIL-101(Cr)-X对氮的吸附能力显著提高。对于MIL-101(Cr)-NO，零覆盖度下氮的吸附焓为30.01 kJ/mol，远大于MIL-101(Cr)-CH的吸附焓（14.31 kJ/mol）。红外光谱研究、巴德电荷和密度泛函理论计算表明，-NO的存在可增强Cr(III)金属不饱和位点的路易斯酸度，从而导致对氮有很强的相互作用亲和力。吸附等温线表明，MIL-101(Cr)-NO对N/O（79/21，v/v）具有高达10.8的优异选择性以及良好的N/CH分离性能（S = 2.8，298 K，1 bar）。突破曲线表明，MIL-101(Cr)-NO在高效分离N/O和N/CH方面具有巨大潜力。
