A highly porous 4,4-paddlewheel-connected NbO-type metal–organic framework with a large gas-uptake capacity

Abstract

A highly porous 4,4-paddlewheel-connected NbO-type metal–organic framework (HNUST-2, HNUST represents Hunan University of Science and Technology) has been designed and synthesized by self-assembling [Cu₂(COO)₄] SBUs with a nanosized tetracarboxylate ligand prolonged by alkyne groups, 5,5′-(naphthalene-1,4-diylbis(ethyne-2,1-diyl))diisophthalic acid (H₄NDED). HNUST-2 exhibits high structural stability, a porous non-interpenetration framework with open metal sites and excellent gas-uptake capacity. This MOF material possesses a high BET surface area of 2366 m² g⁻¹, a large unsaturated excess and total H₂ uptake of 4.57 wt% and 5. 20 wt% at 20 bar and 77 K, respectively. Meanwhile, HNUST-2 also exhibits an excellent adsorption capacity for CO₂ (18.07 mmol g⁻¹ at 20 bar and 298 K) and CH₄ (85.6 cm³ cm⁻³ at 20 bar and 298 K) with a high selectivity for CO₂ over N₂ (22.9) and CH₄ (4.9) at 298 K.