No abstract

Propylsulfonic acid (PrSO3H) derivatised solid acid catalysts have been prepared by post‐modification of mesoporous SBA‐15 silica with mercaptopropyltrimethoxysilane (MPTMS), and the impact of co‐derivatisation with octyltrimethoxysilane (OTMS) groups to impart hydrophobicity to the catalyst was investigated. Turnover frequencies (TOFs) for acetic acid esterification with methanol increase with PrSO3H surface coverage across both families, suggesting a cooperative effect between adjacent acid sites at high acid site densities. Esterification activity is further promoted upon co‐functionalisation with hydrophobic octyl chains, with inverse gas chromatography (IGC) measurements indicating that the increased activity correlates with decreased surface polarity or increased hydrophobicity.

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The morphology of cross-linked polymers plays an important role in their physical and chemical properties. NMR cryoporometry allows for the investigation of these structures over different length scales, through appropriate choice of probe liquid. The different structures of two different polymeric samples, one a cross-linked polymer hydrogel, the other a pore-expanded ion-exchange polymer, are analysed here. The ability for NMR cryoporometry to analyse both polymeric materials in the swollen state is successfully demonstrated, as is the importance of probe-liquid choice for the analysis of different regions of the pore structure. In both cases, water is used to identify populations of pores smaller than ca. 5 nm. The use of t-butanol and menthol reveals the presence of additional mesoporous structures in the ionexchange resin as well as the responsiveness of the pore structure to the liquid used to swell it.

Recyclable PdCu single atom alloys supported on Al2O3 were applied to the selective hydrogenation of crotonaldehyde to elucidate the minimum number of Pd atoms required to facilitate the sustainable transformation of an α,β-unsaturated carbonyl molecule. It was found that, by diluting the Pd content of the alloy, the reaction activity of Cu nanoparticles can be accelerated, enabling more time for the cascade conversion of butanal to butanol. In addition, a significant increase in the conversion rate was observed, compared to bulk Cu/Al2O3 and Pd/Al2O3 catalysts when normalising for Cu and Pd content, respectively. The reaction selectivity over the single atom alloy catalysts was found to be primarily controlled by the Cu host surface, mainly leading to the formation of butanal but at a significantly higher rate than the monometallic Cu catalyst. Low quantities of crotyl alcohol were observed over all Cu-based catalysts but not for the Pd monometallic catalyst, suggesting that it may be a transient species converted immediately to butanol and or isomerized to butanal. These results demonstrate that fine-tuning the dilution of PdCu single atom alloy catalysts can leverage the activity and selectivity enhancement, and lead to cost-effective, sustainable, and atom-efficient alternatives to monometallic catalysts.

The electronic effects of supports on immobilized organometallic complexes impact their activity and lifetime, yet remain poorly understood. Here we describe a systematic study of the support effects experienced by an organometallic complex immobilized on doped hydrotalcite-like materials. To that end, we describe the synthesis and characterization of the first organometallic species immobilized on a palette of doped hydrotalcites via sulfonate linkers. The organometallic species consists of iridium N -heterocyclic carbene (NHC) carbonyl complex ([Na][Ir-(NHC-Ph-SO 3 ) 2 (CO) 2 ]), a highly active molecular catalyst for transfer hydrogenation of glycerol. The hydrotalcite supports are composed of Al, Mg, and a compatible transition-metal dopant (Fe, Cu, Ni, Zn). The materials were characterized extensively by STEM, XPS, TGA, PXRD, FT-IR, N 2 desorption, ICP-AES, TPD, and microcalorimetry to probe the morphology and electronic properties of the support and elucidate structure–property relationships.