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

Ru-HKUST-1 (Ru₃(btc)₂X_1.5; btc^3– = 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)_1.07Cl_0.43, as prepared under our conditions. Furthermore, simply treating the sample as air-sensitive upon isolation greatly improved the adsorption selectivities toward unsaturated molecules.