Gold Nanoparticles on 3D-Printed Filters: From Waste to Catalysts.

Three-dimensionally printed solid but highly porous polyamide-12 (PA12) plate-like filters were used as selective adsorbents for capturing tetrachloroaurate from acidic solutions and leachates to prepare PA12-Au composite catalysts. The polyamide-adsorbed tetrachloroaurate can be readily reduced to gold nanoparticles by using sodium borohydride, ascorbic acid, hydrogen peroxide, UV light, or by heating. All reduction methods led to polyamide-anchored nanoparticles with an even size distribution and high dispersion. The particle sizes were somewhat dependent on the reduction method, but the average diameters were typically about 20 nm. Particle sizes were determined by using a combination of single-particle inductively coupled plasma mass spectrometry, helium ion microscopy, and powder X-ray diffraction. Dispersion of the particles was analyzed by scanning electron microscopy with energy-dispersive spectroscopy. Due to the high adsorption selectivity of polyamide-12 toward tetrachloroaurate, the three-dimensional-printed filters were first used as selective gold scavengers for the acidic leachate of electronicwaste (WEEE). The supported nanoparticles were then generated directly on the filter via a simple reduction step. These objects were used as catalysts for the reduction of 4-nitrophenol to 4-aminophenol. The described method provides a direct route from waste to catalysts. The selective laser sintering method can be used to customize the flow properties of the catalytically active filter object, which allows the optimization of the porous catalytic object to meet the requirements of catalytic processes.

Group 13 complexes of dipyridylmethane, a forgotten ligand in coordination chemistry.

The reactions of dipyridylmethane (dpma) with group 13 trichlorides were investigated in 1 : 1 and 1 : 2 molar ratios using NMR spectroscopy and X-ray crystallography. With 1 : 1 stoichiometry and Et2O as solvent, reactions employing AlCl3 or GaCl3 gave mixtures of products with the salt [(dpma)2MCl2](+)[MCl4](-) (M = Al, Ga) as the main species. The corresponding reactions in 1 : 2 molar ratio gave similar mixtures but with [(dpma)MCl2](+)[MCl4](-) as the primary product. Pure salts [(dpma)AlCl2](+)[Cl](-) and [(dpma)AlCl2](+)[AlCl4](-) could be obtained by performing the reactions in CH3CN. In the case of InCl3, a neutral monoadduct (dpma)InCl3 formed regardless of the stoichiometry employed. A neutral adduct (dpma)(BCl3)2 was obtained from the reaction between dpma and BCl3 in Et2O using 1 : 2 stoichiometry. With 1 : 1 molar ratio of reagents, a mixture of products and deprotonation of the methylene bridge in [(dpma)BCl2](+) was observed. The experimental data showed that the structural flexibility of the dpma ligand results in more diverse coordination chemistry with group 13 elements than that observed for bipyridine (bpy), while computational investigations indicated that the investigated metal-ligand interactions are, to a first approximation, independent of the ligand type. Electrochemical and chemical attempts to reduce the cations [(dpma)MCl2](+) showed that, in stark contrast to the chemistry of the related [(bpy)BCl2](+) cation, the neutral radicals [(dpma)MCl2]˙ are extremely unstable. Differences in the redox behaviour of dpma and bpy could be rationalized with the electronic structure of the ligand and that of the methylene bridge in particular. As a whole, the facile reactivity of the methylene bridge in the dpma ligand renders it amenable to further reactivity and functionalization that is not possible in the case of bpy.