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A palladium diphosphine pincer complex H3(PNNNP-PdI) has been encapsulated in the benzotriazolate metal-organic framework MFU-4l-OH ([Zn5(OH)4(btdd)3], btdd2− = bis(1,2,3-triazolo)dibenzodioxin), and the resulting materials were investigated as Lewis acid catalysts for cyclization of citronellal to isopulegol. Rapid catalyst immobilization is facilitated by a Brønsted acid–base reaction between the H3(PNNNP-PdI) benzoic acid substituents and Zn–OH groups at the framework nodes. Catalyst loading can be controlled up to a maximum of 0.5 pincer complexes per formula unit [ PdI-x , Zn5(OH)4−nx(btdd)3(H3−nPNNNP-PdI)xx = 0.06–0.5, n ≈ 2.75]. Oxidative ligand exchange was used to replace I− with weakly coordinating BF4− anions at the Pd–I sites, generating the activated PdBF4-x catalysts (x = 0.06, 0.10, 0.18, 0.40). The Lewis acid catalytic activity of the PdBF4-x series decreases with increasing catalyst density as a result of the appearance of mass transport limitations. Initial catalytic rates show that the activity of PdBF4-0.06 approaches the intrinsic activity of a homogeneous PNNNP-PdBF4 catalyst analogue. In addition, PdBF4-0.06 exhibits better catalytic activity than the metallolinker-based MOF Zr-PdBF4 and was not subject to leaching or catalyst degradation processes observed for the homogeneous analogue. [ABSTRACT FROM AUTHOR]

Functionalized metal–organic frameworks (MOFs) have been used in a wide range of applications. Although the development of functionalized MOFs with plentiful open metal sites (defects) provides an avenue for targeted reactions, creating such defects remains challenging. Herein, a UiO-type MOF with hierarchical porosity and plentiful Zr–OH/OH2 sites (capping 35% Zr coordination sites) was synthesized within 40 min by a solid-phase synthesis route without the use of solvent and template. The optimal sample converted 5.7 mmol benzaldehyde to (dimethoxymethyl)benzene within 2 min at 25 °C. The turnover frequency number and activity per unit mass reached 2380 h−1 and 8568 mmol g−1 h−1, respectively, outperforming all previously reported catalysts at room temperature. This excellent catalytic activity was correlated with the defect density in functionalized UiO-66(Zr) and the accessibility of plentiful Zr–OH/OH2 sites as acid sites. [ABSTRACT FROM AUTHOR]

Conversion of 5-hydroxymethylfurfural (HMF) into 5-ethoxymethylfurfural (EMF) and ethyl levulinate (EL) is an attractive biomass transformation due to its potential application in the energy and chemical industries. Here, we report on the conversion with MOF-based polyoxometalate [Cu–BTC][HPM] (NENU-5) as the catalyst. The homogeneous distribution of HPM in the pores of Cu–BTC makes the composite combine the properties of the catalytic activity of HPM and the insolubility, large surface area and hierarchical pores of Cu–BTC. The catalyst demonstrates reusability and catalytic activity with 55% yield of EMF and 11% yield of EL. [ABSTRACT FROM AUTHOR]