New metal-organic framework separates gases with ease

Researchers have developed a type of microporous metal-organic framework (MOF) that displays "exceptional" separation properties in the production of polymer-grade ethylene, a highly important - yet costly to produce - industrial chemical. According to the new study, the new iron-peroxo based MOF is the most effective material yet reported for separating the gases ethane and ethylene, and its use has great potential for industrial applications. Ethylene (C₂H₄), a widely used chemical, is important in the manufacture of many products, like polyethylene plastics. However, the current well-established method of producing the chemical requires its separation from ethane (CC₂H₆) using a cryogenic distillation process, which is one of the most energy-intensive processes in the chemical industry. The development of a cost- and energy-efficient ethylene/ethane separation process is highly desired and is among the most important towards ensuring future energy-efficient industrial separation processes. Gas separation processes based on microporous materials, such as MOFs, have shown to be a promising alternative to traditional ethylene/ethane separation methods. However, many of these materials preferentially capture ethylene, which must be further separated from the MOFs using additional processes. Furthermore, to achieve polymer-grade levels of purity (>99.95%), multiple cycles of separation are required, which limit the related approaches' overall efficiency and cost-effectiveness. Inspired by natural metalloenzymes that contain iron-peroxo sites and preferentially bind alkanes like ethane, Libo Li and colleagues synthesized a similar MOF using FeC₂(OC₂)(dobdc) and evaluated its separation performance. Li et al. found that the material demonstrated a strong preference for binding ethane over ethylene. What's more, the authors show its ability to produce polymer-grade ethylene (99.99%) from a single cycle separation cycle at ambient conditions. The high performance for ethane/ethylene separation was further validated using theoretical calculations, simulations and experiments.

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