Abstract:

The efficient and low-cost removal of trace NF₃ impurities in the preparation of CF₄ by fluorocarbon synthesis method has important application value for the development of electronic grade CF₄. In this paper, a series of MOF-74 materials with high density open metal sites were prepared as adsorbents. Based on the strong interaction of active sites on NF₃ inside the one-dimensional channels, the ultra-high adsorption capacity of NF₃ under low partial pressure (up to 50.3mL/g at 298K and 10kPa) and excellent NF₃/CF₄ selectivity (the IAST selectivity of MOF-74-Mg can reach to 245.6 at 0.001 molar ratio of NF₃) were achieved. The theoretical results showed that the unsaturated metal sites in the pores of MOF-74 had stronger affinity for the polar molecule NF₃, and the fixed-bed breakthrough experiment further verified that the materials could capture trace NF₃ in CF₄ under dynamic conditions. In summary, the above results confirmed that MOFs materials with open metal sites could be served as an efficient and economical adsorbent, providing a new strategy for the separation and purification of trace NF₃ impurities in CF₄ prepared by fluorocarbon synthesis.

Key words: opening metal sites, metal organic framework, carbon tetrafluoride, nitrogen trifluoride, electronic special gas purification

摘要：

高效低成本脱除氟碳合成法制备CF₄中的少量NF₃杂质对电子级CF₄的开发有着重要的应用价值。本文制备了一系列具备高密度开放金属位点的MOF-74材料作为吸附剂，利用一维孔道内活性位点与NF₃的强相互作用，在低分压下实现对NF₃的超高吸附容量（298K和10kPa时最高可达50.3mL/g）及优异NF₃选择性（在NF₃与CF₄摩尔比为0.001时，MOF-74-Mg对NF₃的理想吸附溶液理论选择性可达245.6）。理论计算结果表明，MOF-74孔道内的不饱和金属位点对极性分子NF₃具有强的吸附作用力；固定床穿透实验则进一步验证了材料能够在动态条件下捕获CF₄中的痕量NF₃。以上结果证实了这类基于开放金属位点的MOFs材料能够作为一种高效经济型的吸附剂，为分离纯化氟碳合成法制备CF₄中的痕量NF₃杂质提供了一种新的策略。

关键词: 开放金属位点, 金属有机骨架, 四氟化碳, 三氟化氮, 电子特气纯化