Elucidating the Structure of the Metal–Organic Framework Ru-HKUST-1

Ru-HKUST-1 (Ru3(btc)2X1.5; btc3– = 1,3,5-benzenetricarboxylate; X– = chloride, acetate, trimesate, hydroxide) has received considerable attention as a result of its structure type, tunability, and the redox-active nature of its constituent metal paddlewheel building units. When compared to other members of the HKUST-1 family, its surface area is typically reported as ∼25% lower than expected. In contrast to this, a related ruthenium-based porous coordination cage, Ru24(tBu-bdc)24Cl12, displays the expected surface area when compared to Cr2+ and Mo2+ analogs. Here, we examine the factors that result in this decreased surface area for the metal–organic framework (MOF). We show that with appropriate solvent exchange and activation conditions, Ru-HKUST-1 can display a BET surface area as high as 1439 m2/g. We utilize a combination of spectroscopic and diffraction techniques to accurately determine the structure of the MOF, which is most accurately described here as Ru3(btc)2(OAc)1.07Cl0.43, as prepared under our conditions. Furthermore, simply treating the sample as air-sensitive upon isolation greatly improved the adsorption selectivities toward unsaturated molecules.