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 N2 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 Å 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 (≈1808), and CO2/N2 (≈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.