Breaking the trade-off between selectivity and adsorption capacity for gas separation

ABSTRACT: Summary The trade-off between selectivity and adsorption capacity with porous materials is a major roadblock to reducing the energy footprint of gas separation technologies. To address this matter, we report herein a systematic crystal engineering study of C2H2 removal from CO2 in a family of hybrid ultramicroporous materials (HUMs). The HUMs are composed of the same organic linker ligand, 4-(3,5-dimethyl-1H-pyrazol-4-yl)pyridine, pypz, three inorganic pillar ligands, and two metal cations, thereby affording six isostructural pcu topology HUMs. All six HUMs exhibited strong binding sites for C2H2 and weaker affinity for CO2. The tuning of pore size and chemistry enabled by crystal engineering resulted in benchmark C2H2/CO2 separation performance. Fixed-bed dynamic column breakthrough experiments for an equimolar (v/v = 1:1) C2H2/CO2 binary gas mixture revealed that one sorbent, SIFSIX-21-Ni, was the first C2H2 selective sorbent that combines exceptional separation selectivity (27.7) with high adsorption capacity (4 mmol·g−1). Graphical abstract Highlights • Six isostructural hybrid ultramicroporous materials are prepared and characterized• Crystal engineering approach enabled fine-tuning of pore size and chemistry• Weak CO2/strong C2H2 affinity resulted in high C2H2/CO2 separation selectivities• SIFSIX-21-Ni: benchmark selectivity/uptake capacity for C2H2/CO2 separation The bigger picture It is generally recognized that porous solids (sorbents) with high selectivity and high adsorption capacity offer potential for energy-efficient gas separations. Unfortunately, there is generally a trade-off between capacity and selectivity, which represents a roadblock to the utility of sorbents in key industrial processes. For example, acetylene (C2H2), an important fuel and chemical intermediate, is produced with CO2 as an impurity, and the similar physicochemical properties of C2H2 and CO2 mean that most sorbents are poorly selective. Hybrid ultramicroporous materials (HUMs) are candidates for gas separations as they exhibit benchmark selectivity for several key gas pairs. Unfortunately, existing HUMs are handicapped by low capacity. We report a new HUM, SIFSIX-21-Ni, that addresses the trade-off between selectivity and capacity that has plagued sorbents, as its high uptake and high selectivity renders it the new benchmark for C2H2/CO2 separation performance. A new family of six isostructural hybrid ultramicroporous materials that enabled high adsorption capacity as well as high experimental separation selectivity values for C2H2/CO2 separation.

SUBMITTER: Kumar N 

PROVIDER: S-EPMC8600127 | biostudies-literature |

REPOSITORIES: biostudies-literature