甲烷（CH4）中的氮（N2）排出是天然气处理中最具挑战性的步骤，因为它们的物理化学性质非常相似。几十年来，人们努力寻找一种能够选择性区分N2的功能材料，但收效甚微。
该文中，研究人员报道了一种分子活板门分子筛K-ZSM-25，它具有所有分子筛中最大的单胞，能够捕获N2，有利于CH4，选择性高达34。发现该分子筛表现出温度调节的气体吸附，其中气体分子对晶体内部孔隙的可达性取决于气体-阳离子相互作用对“门保持”阳离子热振荡的影响。N2和CH4分子通过不同的准入触发温度进行区分。在240–300 K的温和工作温度范围内，N2气体分子能够进入K-ZSM-25的内部孔隙，而CH4被拒绝。正如实验、分子动力学和从头算密度泛函理论研究所证实的那样，在特定的温度范围内实现了出色的N2/CH4选择性，在该温度范围内，挡门K+的热振荡仅为相对较小的分子（N2）提供了足够的空间扩散到和通过分子筛超笼。
K-ZSM-25活板门分子筛的该温度调节吸附为在天然气工业中从CH4中排出N2开辟了一条新途径，而无需在100 K左右部署能耗高的低温蒸馏。
附：英文原文
Title: Nitrogen Rejection from Methane via a “Trapdoor” K-ZSM-25 Zeolite
Author: Jianhua Zhao, Seyed Hesam Mousavi, Gongkui Xiao, Abdol Hadi Mokarizadeh, Thomas Moore, Kaifei Chen, Qinfen Gu, Ranjeet Singh, Ali Zavabeti, Jefferson Zhe Liu, Paul A. Webley, Gang Kevin Li
Issue&Volume: September 13, 2021
Abstract: Nitrogen (N2) rejection from methane (CH4) is the most challenging step in natural gas processing because of the close similarity of their physical-chemical properties. For decades, efforts to find a functioning material that can selectively discriminate N2 had little outcome. Here, we report a molecular trapdoor zeolite K-ZSM-25 that has the largest unit cell among all zeolites, with the ability to capture N2 in favor of CH4 with a selectivity as high as 34. This zeolite was found to show a temperature-regulated gas adsorption wherein gas molecules’ accessibility to the internal pores of the crystal is determined by the effect of the gas–cation interaction on the thermal oscillation of the “door-keeping” cation. N2 and CH4 molecules were differentiated by different admission-trigger temperatures. A mild working temperature range of 240–300 K was determined wherein N2 gas molecules were able to access the internal pores of K-ZSM-25 while CH4 was rejected. As confirmed by experimental, molecular dynamic, and ab initio density functional theory studies, the outstanding N2/CH4 selectivity is achieved within a specific temperature range where the thermal oscillation of door-blocking K+ provides enough space only for the relatively smaller molecule (N2) to diffuse into and through the zeolite supercages. Such temperature-regulated adsorption of the K-ZSM-25 trapdoor zeolite opens up a new approach for rejecting N2 from CH4 in the gas industry without deploying energy-intensive cryogenic distillation around 100 K.
DOI: 10.1021/jacs.1c06230
Source: https://pubs.acs.org/doi/10.1021/jacs.1c06230
