Novel organically linked ZnII hydrogenselenite coordination polymers: synthesis, characterization, and efficient TiO2 photosensitization for enhanced photocatalytic hydrogen production.

This study focused on the solvothermal synthesis, characterization, and photocatalytic activities of two novel coordination polymers, namely [Zn(µ-HSeO3)2(bipy)]n (1) and [Zn(µ-HSeO3)2(phen)]n (2). These compounds represent the first organically linked ZnII hydrogenselenite coordination polymers. The synthesis of compounds 1 and 2 involved the addition of 2,2'-bipyridine and 1,10-phenanthroline, respectively, to SeO2 and ZnO in methanol as the solvent. The novel hydrogenselenite compounds were thoroughly characterized using spectroscopic and crystallographic methods. The photocatalytic solids (TiO2-1A and TiO2-2A) were prepared by immobilizing compounds 1-2 onto TiO2 through the sol-gel approach. These photocatalysts were then evaluated for hydrogen evolution via water splitting using a 300 W Hg/Xe lamp as the irradiation source. Among the newly synthesized photocatalytic materials, TiO2-1A demonstrated auspicious photocatalytic performance for hydrogen gas production. Its catalytic activity overcame the observed for the pure solid support TiO2 and Degussa P25 (commercial titania), making compound 1 a particularly attractive TiO2 photosensitizer. Additionally, TiO2-1A exhibited superior photocatalytic activity compared to TiO2-2A. The latter performed better than freshly prepared TiO2, approaching that of Degussa P25. These findings highlight the potential of compound 1 as an effective photosensitizer for TiO2-based photocatalysis, making it a promising candidate for applications in clean energy generation, specifically in hydrogen production by water splitting.

Polymer-coated palladium nanoparticle catalysts for Suzuki coupling reactions.

A set of seven different palladium nanoparticle (PdNP) systems stabilized by small amounts (1.0mg/mL) of structurally related macromolecular capping agents were comparatively tested as catalyst in p-nitrophenol (Nip) reduction and Suzuki cross-coupling reactions. The observed rate constants (kobs) for Nip reduction were in the range of 0.052-3.120×10(-2)s(-1), and the variation reflected the effects of polymer chain conformation, ionic strength and palladium-polymer complex coordination. Macromolecules featuring pendant pyridyl moieties or inverse temperature-dependent solubility were found to be unsuitable capping agents for PdNPs catalysts, despite being active. The catalytic activity in Suzuki cross-coupling reactions followed the same behavior; the most active particles in the Nip reaction also mediated the cross-coupling reaction providing the expected products in quantitative yields under relatively mild conditions after only 4h at 50°C. Experiments involving the successive addition of reactants and catalyst recovery/re-use indicated that the recycling potential was comparable to those of the standards used in this field.