Korean Journal of Materials ResearchISSN:1225-0562(Print) 2287-7258(Online)한국재료학회

Nitrogen is a serious contaminant in natural gas because it decreases the energy density. The natural gas specification in South Korea requires a N₂ content of less than 1 mol%. Thus, cost-effective N₂ removal technology from natural gas is necessary, but until now the only option has been energy-intensive processes, e.g., cryogenic distillation. Using porous materials for the removal process would be beneficial for an efficient separation of CH₄/N₂ mixtures, but this still remains one of the challenges in modern separation technology due to the very similar size of the components. Among various porous materials, metal-organic frameworks (MOFs) present a promising candidate for the potential CH₄/N₂ separation material due to their unique structural flexibility. A MIL-53(Al), the most well-known flexible metal-organic framework, creates dynamic changes with closed pore (cp) transitions to open pores (ops), also called the ‘breathing’ phenomenon. We demonstrate the separation performance of CH₄/N₂ mixtures of MIL-53(Al) and its derivative MIL-53-NH₂. The CH₄/N₂ selectivity of MIL-53-NH₂ is higher than pristine MIL-53(Al), suggesting a stronger CH₄ interaction with NH₂.