Heterogenised Rh(I), Ir(I) metal complexes with chiral triaza donor ligands: a cooperative effect between support and complex

Prototype Atomically Dispersed Supported Metal Catalysts: Iridium and Platinum

When metal nanoparticles on supports are made smaller and smaller-to the limit of atomic dispersion-they become cationic and take on new catalytic properties that are only recently being discovered. The synthesis of these materials is reviewed, including their structure characterization-especially by atomic-resolution electron microscopy and X-ray absorption and infrared spectroscopies-and relationships between structure and catalyst performance, for reactions including hydrogenations, oxidations, and the water gas shift. Structure determination is challenging because of the intrinsic nonuniformity of the support surfaces-and therefore the structures on them-but fundamental understanding has advanced rapidly, benefiting from nearly uniform catalysts consisting of metals on well-defined-crystalline-supports and their characterization by spectroscopy and microscopy. Recent advances in atomic-resolution electron microscopy have spurred the field, providing stunning images and deep insights into structure. The iridium catalysts have typically been made from organoiridium precursors, opening the way to understanding and control of the metal-support bonding and ligands on the metal, including catalytic reaction intermediates. Platinum catalysts are usually made with less precision, from salt precursors, but they catalyze a wider array of reactions than the iridium, typically being stable at higher temperatures and seemingly offering rich prospect for discovery of new catalysts.

Synthesis and Characterization of Organofunctionalized MCM-41 by the Original Stepped Templated Sol−Gel Technology

Four types of organofunctionalized (by phenyl, 3-aminopropyl, 3-chloropropyl, and N-aminoethylaminopropyl, respectively) mesoporous silicates MCM-41 (hereafter R-MCM-41) have been successfully synthesized via the grafting method, the conventional templated sol-gel technology, and the original stepped templated sol-gel technology. The prepared inorganic-organic hybrid materials were characterized in detail by powder X-ray diffraction (XRD), 29Si and 13C MAS NMR spectrometry, isothermal nitrogen adsorption-desorption analysis, FT-IR spectrometry including in situ drift technique, and thermogravimetric analysis (TGA). Through a series of investigations and comparisons, the advantageous stepped templated sol-gel technology introduced in this paper is demonstrated to be a remarkable approach that gathers the superior properties of the current grafting method and the conventional hydrothermal co-condensation synthesis, yielding as a consequence both thermodynamically firm fixation and relatively large content of organic functional species on the MCM-41 support. The novel synthetic strategy also evidently shortens the crystallization time for the organofunctionalized MCM-41 with regular specific structure.