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

Abstract

The efficient separation of C 2 H 2 from C 2 H 2 /CO 2 or C 2 H 2 /CO 2 /CH 4 mixtures is crucial for achieving high-purity C 2 H 2 (>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 C 2 H 2 /CO 2 and C 2 H 2 /CO 2 /CH 4 separation. The framework, partitioned by fluorinated SiF 6 2– anions into three distinct cages, enables both a high C 2 H 2 capacity (176.5 cm 3 /g at 298 K and 1.0 bar) and outstanding C 2 H 2 selectivity over CO 2 (13.4) and CH 4 (233.5) simultaneously. Notably, we achieve a record-high C 2 H 2 productivity (132.7, 105.9, 98.8, and 80.0 L/kg with 99.5% purity) from C 2 H 2 /CO 2 (v/v = 50/50) and C 2 H 2 /CO 2 /CH 4 (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 C 2 H 2 and two hexafluorosilicate (SiF 6 2– ) anions in the confined cavities.