A Two-Dimensional Stacked Metal-Organic Framework for Ultra Highly-Efficient CO2 Sieving

Carbon capture from flue gas and natural gas benefits to make the most of resource gases and alleviate global warming, though achieving ultra-high selectivities to sieve CO2 from CH4 and N-2 remains a challenge. To this end, MOFs with delicate size-exclusive pores and inherent functional groups may give birth to efficient CO2 sieving sorbents, with intriguing CO2 selectivities and capacities. Herein, we report a two-dimensional stacked indium-based MOF, i.e., In(aip)(2), with functional -NH2 groups and channels around 3.57 angstrom to specifically trap CO2, with a uptake over 1.27 mmol/g at 298 K and 101 kPa. Indeed, In(aip)(2) possesses amazingly-high IAST selectivities for CO2/CH4 (approximate to 1808), and CO2/N-2 (approximate to 2635) at 298 K and 101 kPa, at least a magnitude superior to most of other MOF materials reported to date. The following static/dynamic sorption measurements corroborated the separation properties of this material, with purity gas (ca. 99 %) of CO2 once released. In-depth theoretical calculations further demonstrated the host-guest interactions, as facilitated by hydrogen bonding, for CO2 sieving. Our principle to design and identify MOF materials in this study proved an inspiring route to prepare highly-efficient CO2 sieving sorbents.