Controlled SBU Approaches to Isoreticular Metal-Organic Framework Ruthenium-Analogues of HKUST-1

A controlled secondary building unit approach (CSA) was employed to obtain a series of ruthenium metal-organic frameworks (MOFs) of the general formula [Ru-3(BTC)(2)X-x]G(g) (BTC = 1,3,5-benzenetricarboxylate; X = counter-anion, G = guest molecules) which are structural analogues of [M-3(BTC)(2)] (M = Cu, Zn, Ni, Cr, Mo). The compounds [Ru-2(OOCR)(4)X] and [Ru-2(OOCCH3)(4)]Y were varied as Ru sources for CSA; namely strong coordinating X (Cl-) and weakly coordinating Y ([BF4](-) or [BPh4](-)) as well as the alkyl groups at the carboxylate ligand [R = CH3 or C(CH3)(3)] were utilized. Four phase-pure Ru-MOFs were obtained: [Ru-3(BTC)(2)Cl-0.5(OH)](AcOH)(1.5) (1), [Ru-3(BTC)(2)Cl-1.2(OH)(0.3)](H3BTC)(0.15)(AcOH)(2.4)(PivOH)(0.45) (2), [Ru-3(BTC)(2)F-0.5(OH)](AcOH)(1.0) (3) and [Ru-3(BTC)(2)(OH)(1.5)](H3BTC)(0.5)(AcOH)(1.4) (4) {AcOH = CH3COOH, PivOH = (CH3)(3)CCOOH}. The series of characterization data support the analytical composition and isostructural nature of 1-4, i.e. powder X-ray diffraction (PXRD), IR- and H-1-NMR spectroscopy, thermal gravimetric analysis (TGA) and N-2 sorption were employed. The valence state of the Ru-sites were studied by X-ray absorption spectroscopy (XAS). The chosen precursors for CSA and optimized synthesis, work-up and activation protocols allowed improvement of the overall crystallinity, purity (i.e., residual solvent molecules) and surface area of the Ru-MOF materials.