Directed assembly of a high surface area 2D metal–organic framework displaying the augmented “kagomé dual” (kgd-a) layered topology with high H2 and CO2 uptake

Abstract

The rigid and highly aromatic hexatopic, carboxylate-based organic linker H₆L, under solvothermal reaction conditions with CoCl₂·6H₂O, directs the assembly of two new 2D MOFs (denoted as 1 and 2) with the rare kgd-a layered topology, as revealed by single crystal X-ray diffraction measurements. A unique 3-connected dinuclear cluster, Co₂(–COO)₃Cl, was observed in 1 and this MOF was found to be stable upon solvent removal, in contrast to 2, where single Co²⁺ cations serve as 3-c nodes and the structure collapses upon activation. A detailed Ar sorption measurement at 87 K revealed that 1 has an apparent BET surface area of 1299 m² g⁻¹ with narrow pore size distribution, centered at 6.9 Å. A very high H₂ and CO₂ uptake is observed reaching 209.9 cm³ (STP) g⁻¹ and 106.8 cm³ (STP) g⁻¹ at 77 K/1 bar and 273 K/1 bar, respectively, which is attributed to the combination of small pore size and the high density of aromatic rings in 1.