Gold nanoparticles (AuNP) are widely used for reaction catalysis. The common understanding is that the smaller the particles, the more reactive they are. It is reported here that this is not always the case for citrate (Ct) or polyvinylpyrrolidone (PVP) stabilized AuNP in the catalytic reduction of 4‐nitrophenol with sodium borohydride (NaBH4), when the total surface area is kept constant. The results prove that for AuNP in the size range of 10–58 nm, the reactivity increases with increasing particle diameter for the investigated model reaction. The trend of catalytic activity is independent of the conjugated ligands for citrate and PVP ligands. Purely based on size and resulting surface area, the trend in catalytic activity is unexpected. Only a more detailed structural investigation revealed that internal structure parameters like defect tendency also play a strong role. Larger AuNP possess more defects between crystalline domains. Further, the influence of the ligand density on the surface of AuNP and the diffusion effect of reactants are excluded for the nitrophenol reduction.
In this work, we provide a systematic kinetic study on the influence of the patchy structure of electrospun hybrid nonwovens on their catalytic activity in the gold nanoparticle (Au NP)-catalysed alcoholysis of dimethylphenylsilane in n-butanol.
Precise and directt wo-dimensional( 2D) printing of the incompatible polymer acid-base catalysts and their utility in one-pot two-step reactions were shown. Multistep catalytic reactionsu sing incompatible catalysts in ao ne-pot reactionc ascade requires special methods and materials to isolate the catalysts from each other.I ng eneral, this is at edious process requiring special polymer architectures as the carrier fort he catalystst op reserve the activity of otherwise incompatible catalysts.W ep ropose the immobilization of incompatible polymer catalysts,s uch as polymer acid and base catalysts, on as ubstrate in variable sizes and amounts by precise 2D printing.T he terpolymersw ith basic (4-vinylpyridine) and acidic (styrene sulfonic acid) functionalities and methacryloyl benzophenone as aU Vc ross-linkingu nit were used for 2D printing on poly(ethylenet erephthalate) (PET).T he printed meshes were immersed together in ar eactions olutionc ontaining (dimethoxymethyl)benzenea nd ethyl cyanoformate, resulting in at wo-step acid-base catalyzed cascader eaction;t hat is, deacetalization followed by carbon-building reaction. The time-dependent consumption of (dimethoxymethyl)benzenet ot he intermediate benzaldehyde and the product was monitored, and ak ineticm odel was developed to investigate the underlying reaction dynamics. The complexity of multistep Wolf-Lamb-type reactions was generally significantly decreased by using our approachb ecause of the easy polymerization and immobilization procedure. [a] M. O. Pretscher,P rof. Dr.S.A garwal Macromolecular ChemistryI I, Bavarian Polymer Institute Supporting information and the ORCID identification number(s) for the author(s) of this articlecan be found under: https://doi.
A process for preparing active, strong base and acid selfstanding individual membranes and printed structures is established by electrospinning and two-dimensional (2D) printing of the corresponding polymeric base and polymeric acid on a neutral plastic substrate. The active polymeric acid and strong base used in this work were (poly(styrene-co-styrene sulfonic acid-co-methacryloyl benzophenone)) and poly(styrene-co-4-vinylbenzylamine-co-N-(4-benzoylphenyl)acrylamide), respectively. The active acid−base printed structures and membranes were compared for their activity in a standard two-step acidcatalyzed deacetalization reaction of dimethoxybenzyl acetal to benzaldehyde followed by a base-catalyzed Knoevenagel condensation with ethyl cyanoacetate toward ethyl-2-cyano-3-phenyl acrylate reaction in one pot in different solvents. Both 2D-printed acid−base structures and electrospun membranes could be arranged in one pot to complete the two-step reaction without destroying each other's activity. High conversions, fast reaction, and reusability make 2D-printed structures favorable in toluene over electrospun membranes. The kinetic parameters were also calculated to address the solvent's influence and further strengthen the systems' understanding and comparison.
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