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

• The tailored pore size of In(aip) 2 was constructed from staggered stacking of layers; • In(aip) 2 shows over 10 3 IAST selectivities for both CO 2 /CH 4 and CO 2 /N 2 mixtures, • In(aip) 2 reveals a highly-efficient, ca. 99 %, capture of CO 2 from CH 4 and N 2 . 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 CO 2 from CH 4 and N 2 remains a challenge. To this end, MOFs with delicate size-exclusive pores and inherent functional groups may give birth to efficient CO 2 sieving sorbents, with intriguing CO 2 selectivities and capacities. Herein, we report a two-dimensional stacked indium-based MOF, i.e., In(aip) 2 , with functional –NH 2 groups and channels around 3.57 Å to specifically trap CO 2 , with a uptake over 1.27 mmol/g at 298 K and 101 kPa. Indeed, In(aip) 2 possesses amazingly-high IAST selectivities for CO 2 /CH 4 (≈1808), and CO 2 /N 2 (≈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 CO 2 once released. In-depth theoretical calculations further demonstrated the host–guest interactions, as facilitated by hydrogen bonding, for CO 2 sieving. Our principle to design and identify MOF materials in this study proved an inspiring route to prepare highly-efficient CO 2 sieving sorbents.