MOFs of general composition [M₆(OH)₄(O)₄(PDC)_6−x(Cl)_2x(H₂O)_2x] with M = Zr, Ce, Hf; and 0 ≤ x ≤ 2 were obtained and characterised in detail.

The metal–organic framework compound [Al(OH)(BDC-Br)] (1) (BDC-Br²⁻ = 5-bromo-1,3-benzenedicarboxylate) denoted CAU-10-Br was synthesised under solvothermal reaction conditions. Its structure was successfully refined by Rietveld methods. The framework is based on the connection of infinite helical chains of cis-corner-sharing AlO₆-polyhedra via BDC-Br²⁻ ions. Thus non-intersecting parallel channels are formed, each periodically varying in diameter between 1.1 and 6.6 Å. Nevertheless 1 adsorbs CO₂ at 298 K, while it is non-porous towards H₂ and N₂ at 77 K. Employing high-throughput (HT) methods we identified synthesis conditions that lead to the formation of mixed-linker MOFs with CAU-10 topology. Starting with a molar ratio H₂BDC : H₂BDC-Br = 3 : 1 we established a synthesis procedure for the partially bromo-functionalised mixed-linker-MOF [Al(OH)(BDC)_0.8(BDC-Br)_0.2] (2) denoted as CAU-10-H/Br. Starting with a molar ratio H₂BDC-NH₂ : H₂BDC-NO₂ = 1 : 1 the partially NO₂- and NH₂-functionalised mixed-linker MOF [Al(OH)(BDC-NO₂)_0.55(BDC-NH₂)_0.23(BDC-NHCHO)_0.22] (3) denoted as CAU-10-NO₂/NH₂ was synthesised, in which the NH₂-groups were found to be partially formylated. The partial bromo-functionalisation in CAU-10-H/Br (2) leads to a lower sorption capacity in comparison with the parent structure CAU-10-H, while the pore accessibility is comparable. The incorporation of NO₂-, NH₂- and NHCHO-groups in CAU-10-NO₂/NH₂ (3) does not only affect the accessibility of the pores for N₂, but results also in an increased capacity for H₂ and CO₂ in comparison with the parent structure CAU-10-NO₂. The reproducibility of the synthesis procedures was tested regarding the composition of the MOFs and the resulting gas sorption properties. In 2 a molar fraction of (BDC)²⁻ = 80 ± 2% is found, while in 3 a molar fraction of (BDC-NO₂)²⁻ = 55 ± 2% is observed. Starting from the molar ratio H₂BDC : H₂BDC-CH₃ = 1 : 1 mixed linker MOFs denoted as CAU-10-H/CH₃ (4) were also obtained. In contrast to 2 and 3 the molar ratios of BDC²⁻/BDC-CH₃ ²⁻ and especially the sorption properties differ substantially for every batch. The compounds were further characterised by X-ray powder diffraction, thermogravimetric/elemental analysis, NMR/Vis/IR-spectroscopy, and gas sorption measurements.

C–H activation reactions are generally associated with relatively low turnover numbers (TONs) and high catalyst concentrations due to a combination of low catalyst stability and activity, highlighting the need for recyclable heterogeneous catalysts with stable single-atom active sites. In this work, several palladium loaded metal–organic frameworks (MOFs) were tested as single-site catalysts for the oxidative coupling of arenes (e.g. o-xylene) via C–H/C–H activation. Isolation of the palladium active sites on the MOF supports reduced Pd(0) aggregate formation and thus catalyst deactivation, resulting in higher turnover numbers (TONs) compared to the homogeneous benchmark reaction. Notably, a threefold higher TON could be achieved for palladium loaded MOF-808 due to increased catalyst stability and the heterogeneous catalyst could efficiently be reused, resulting in a cumulative TON of 1218 after three runs. Additionally, the palladium single-atom active sites on MOF-808 were successfully identified by Fourier transform infrared (FTIR) and extended X-ray absorption fine structure (EXAFS) spectroscopy.

A new inorganic building unit in a Zr-MOF is formed through bridging of the well-known {Zr ₆ O ₄ (OH) ₄ } clusters by (μ-OH) groups.

Development of a flow reactor for facile sub-solvothermal synthesis of MOFs.