In recent years reusable and highly active metal-nanoparticle catalysts were developed for the selective transformation of hydrosilanes into the corresponding silanols using water as the oxidant. The catalysts are much more active than conventional homogeneous ones under ambient conditions. In this perspective, we summarize known catalyst systems as well as stoichiometric methods for the synthesis of silanols from hydrosilanes. Plausible pathways for the hydrolytic oxidation of hydrosilanes on metal nanoparticles are described on the basis of the observations of mechanistic studies, including Si−H bond activation, nucleophilic attack of water (or silanol) at the silicon bonded to metal, and the liberation of silanol (or disiloxane) products. The applications of silanols are classified into usages in organic synthesis and silicon-based materials. Silanols were employed as nucleophilic partners in transitionmetal catalyzed carbon−carbon cross-coupling reactions, organocatalysts for activating carbonyl compounds, intramolecular guiding groups for C−H bond activation reactions, inhibitors of enzymes, and isosteres of bioactive compounds. Various polymeric siliconbased materials were synthesized by the activation of Si−H bonds in bis-trihydrosilanes, bis-hydrosilanes, and polyhedral oligomeric silsesquioxanes (POSS).

The reversible reactions involving formate and bicarbonate can be used to store and release hydrogen (H 2), allowing H 2 to serve as an effective energy carrier in energy systems such as fuel cells. However, to feasibly utilize these reactions for renewable energy applications, efficient catalysts that can reversibly promote both reactions are required. Herein we report the synthesis of novel polyaniline (PANI)derived mesoporous carbon-supported Pd nanoparticles, or materials that can efficiently catalyze these reversible reactions. The synthesis involves pyrolysis of PANI/colloidal silica composite materials at temperatures above 500 °C and then removal of the colloidal silica from the carbonized products with an alkaline solution. The resulting nanomaterials efficiently catalyze the reversible reactions, i.e., the dehydrogenation of formate (HCO 2 ‾ + H 2 O  H 2 + HCO 3 ‾) and the hydrogenation of bicarbonate (H 2 + HCO 3 ‾ H 2 O + HCO 2 ‾). The porosity and the catalytic property of the materials can be tailored, or improved, by changing the synthetic conditions (in particular, the pyrolysis temperature and the amount of colloidal silica used for making the materials). The study further reveals that having an optimum density of N dopant species in the catalysts makes Pd to exhibit high catalytic activity toward both reactions. Among the different materials studied here, the one synthesized at 800 °C with relatively high amount of colloidal silica templates gives the best catalytic activity, with a turnover frequency (TOF) of 2,562 h-1 for the dehydrogenation reaction and a turnover number (TON) of 1,625 for the hydrogenation reaction. These TOF and TON values are currently among the highest values reported for heterogeneous catalysts for these reversible reactions.

A postsynthetic protocol of functionalizing the preformed hollow nanoparticles with metal nanocrystals was developed based on galvanic replacement reaction on the Mn3O4 surface inside the cavity. The developed protocol produced hollow nanoreactor systems, in which a high density of ultrafine catalytic nanocrystals of a range of noble metals, such as Pd, Pt, Rh, and Ir and their alloys, are dispersively immobilized on an interior surface enclosed by a selectively permeable silica shell. The fabricated hollow nanoreactor exhibited highly enhanced activity, selectivity, and recyclability in catalyzing the oxidation of hydrosilanes, which are attributable to the synergistic combination of the porous silica nanoshell and the oxide-immobilized catalyst system.

A series of Pd/SBA-15-amine materials (where “Amine” is primary amine, secondary amine and tertiary amine) containing Pd nanoparticles are synthesized and their catalytic properties for formic acid dehydrogenation are investigated.

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