No abstract

Phase-pure crystalline thin films of a mixed-valence Ru(2)(II,III) metal-organic framework with 1,3,5-benzenetricarboxylate (btc) as a linker were solvothermally grown on amorphous alumina and silica surfaces. Based on the Rietveld refinement, the structure of Ru-MOF was assigned to be analogous to [Cu(3)(btc)(2)] (HKUST-1).

The doping of [Al(OH)L]n [L = 1,4‐benzenedicarboxylate (bdc) or 1,4‐naphthalenedicarboxylate (ndc)] with vanadium ions yields crystalline porous mixed‐metal solid‐solution metal–organic frameworks (MOFs) of general formula [(AlOH)1–x(VO)xL]n (x can be varied in the whole range from 0 to 1). Several characterization methods, including powder X‐ray diffraction (PXRD), electron paramagnetic resonance (EPR), solid‐state NMR and FTIR spectroscopy, strongly support the effective incorporation of vanadium cations. The Al/V‐doped MOFs are isostructural to the parent monometallic MOFs and show a characteristic uniform dependence of the cell parameters on the metal ratios. Detailed spectroscopic investigation provided evidence that the introduced species are fairly well ordered. Interestingly, for low amounts of doped vanadium for both activated and as‐synthesized Al/V phases, the EPR results revealed the presence of vanadyl units as local defects in pseudo‐octahedral or square‐pyramidal environments, which are different from those in the parent MIL‐47(V). This observation matches the nonlinear response of the adsorption properties on variation of the composition. Remarkably, the presence of such mixed Al/V chains strongly affects the breathing behaviour of the materials. Both CO2 sorption and in situ PXRD studies validated a gradual change from highly flexible (with easily induced phase transitions) to totally rigid structures upon increasing vanadium content.

The mixed-valence metal−organic framework [Ru 3 II,III -(btc) 2 Cl 1.5 ] (Ru-MOF) was synthesized by the controlled SBU approach and characterized by combined powder XRD, XPS, and FTIR methods. The interaction of CO molecules with Ru-MOF was studied by a novel instrumentation for ultra-high-vacuum (UHV) FTIR spectroscopy. The high-quality IR data demonstrate the presence of two different CO species within the framework: a strongly bonded CO showing a low-lying band at 2137 cm −1 and a second CO species at 2171 cm −1 with a lower binding energy. It was found that these IR bands cannot be assigned in a straightforward manner to CO molecules adsorbed on the coordinatively unsaturated Ru II site (CUS) and Ru III site connected to an additional Cl − ion for charge compensation. The accurate DFT calculations reveal that the structural and electronic properties of the mixed-valence Ru-MOF are much more complex than expected. One of the Cl − counterions could be transferred to a neighboring paddle-wheel, forming an anionic SBU blocked by two Cl − counterions, whereas the other positively charged paddle-wheel with a Ru 2 II,III dimer exposes two "free" CUS, which can bind two CO molecules with different frequencies and binding energies.

A controlled secondary building unit approach (CSA) was employed to obtain a series of ruthenium metal-organic frameworks (MOFs)