Metal–Organic Framework with Space-Partition Pores by Fluorinated Anions for Benchmark C₂H₂/CO₂ Separation

Abstract

The efficient separation of C₂H₂ from C₂H₂/CO₂ or C₂H₂/CO₂/CH₄ mixtures is crucial for achieving high-purity C₂H₂ (>99%), essential in producing contemporary commodity chemicals. In this report, we present ZNU-12, a metal-organic framework with space-partitioned pores formed by inorganic fluorinated anions, for highly efficient C₂H₂/CO₂ and C₂H₂/CO₂/CH₄ separation. The framework, partitioned by fluorinated SiF₆^2- anions into three distinct cages, enables both a high C₂H₂ capacity (176.5 cm³/g at 298 K and 1.0 bar) and outstanding C₂H₂ selectivity over CO₂ (13.4) and CH₄ (233.5) simultaneously. Notably, we achieve a record-high C₂H₂ productivity (132.7, 105.9, 98.8, and 80.0 L/kg with 99.5% purity) from C₂H₂/CO₂ (v/v = 50/50) and C₂H₂/CO₂/CH₄ (v/v = 1/1/1, 1/1/2, or 1/1/8) mixtures through a cycle of adsorption-desorption breakthrough experiments with high recovery rates. Theoretical calculations suggest the presence of potent "2 + 2" collaborative hydrogen bonds between C₂H₂ and two hexafluorosilicate (SiF₆^2-) anions in the confined cavities.