Kohsuke Mori

Photocatalytic reduction of CO2 with H2O on various titanium oxide photocatalysts

The specific features of the photocatalytic reduction of CO2 with H2O on various types of active titanium oxide catalysts are reviewed. UV-light irradiation of the bulk TiO2 powders in the presence of CO2 and H2O at room temperature under heterogeneous gas-solid conditions produced CH4 as the major product, while the predominant formations of CH3OH as well as CH4 were observed on the highly dispersed titanium oxide moiety anchored on zeolites and mesoporous silica materials. The CH3OH formation is originated from the unique properties of the charge transfer excited state, i.e., (Ti3+–O−)* of the tetrahedrally-coordinated titanium oxide species within the silica frameworks.

The Synthesis of Size‐ and Color‐Controlled Silver Nanoparticles by Using Microwave Heating and their Enhanced Catalytic Activity by Localized Surface Plasmon Resonance

Silver nanoparticles (Ag NPs) of various colors were synthesized within the mesopore structure of SBA-15 by using microwave-assisted alcohol reduction. The charge density is partially localized on the surface of these Ag NPs owing to localized surface plasmon resonance. This charge localization results in them having enhanced catalytic activity under visible light irradiation compared to Ag NPs obtained by thermal processes.

Surfactant‐Free Nonaqueous Synthesis of Plasmonic Molybdenum Oxide Nanosheets with Enhanced Catalytic Activity for Hydrogen Generation from Ammonia Borane under Visible Light

Plasmonic materials have drawn emerging interest, especially in nontraditional semiconductor nanostructures with earth-abundant elements and low resistive loss. However, the actualization of highly efficient catalysis in plasmonic semiconductor nanostructures is still a challenge, owing to the presence of surface-capping agents in their synthetic procedures. To fulfill this, a facile non-aqueous procedure was employed to prepare well-defined molybdenum oxide nanosheets in the absence of surfactants. The obtained MoO(3-x) nanosheets display intense absorption in a wide range attributed to the localized surface plasmon resonances, which can be tuned from the visible to the near-infrared region. Herein, we demonstrate that such plasmonic semiconductor nanostructures could be used as highly efficient catalysts that dramatically enhance the hydrogen-generation activity of ammonia borane under visible light irradiation.

Magnetically recoverable heterogeneous catalyst: Palladium nanocluster supported on hydroxyapatite-encapsulated γ-Fe2O3 nanocrystallites for highly efficient dehalogenation with molecular hydrogen

The dechlorination of various organochlorides using atmospheric molecular hydrogen (H2) can be efficiently catalysed by magnetically separable Pd nanoclusters supported on the surface of hydroxyapatite-encapsulated γ-Fe2O3 (PdHAP-γ-Fe2O3). For instance, dechlorination of chlorobenzene gave benzene with an excellent turnover frequency (TOF) of 2500 h−1 in the presence of 1 atm of H2. This PdHAP-γ-Fe2O3 catalyst can be recovered briefly using an external magnetic field and reused at least three times without loss of its high catalytic activity.

Highly efficient dehydrogenation of indolines to indoles using hydroxyapatite-bound Pd catalyst

A hydroxyapatite-bound palladium catalyst was found to be effective for the dehydrogenation of various types of indolines to give the corresponding indoles. Moreover, the catalyst was readily recovered from the reaction mixture, and could be reused without any loss of its catalytic activity.

Efficient heterogeneous oxidation of organosilanes to silanols catalysed by a hydroxyapatite-bound Ru complex in the presence of water and molecular oxygen

RuHAP is a highly selective and reusable catalyst for the oxidation of a wide variety of organosilanes to the corresponding silanols in the presence of water and molecular oxygen.

Harnessing single-active plasmonic nanostructures for enhanced photocatalysis under visible light

The past several decades have witnessed the fast-growing field of plasmonics, which localize and concentrate incident light at the nanoscale and provide a source of light, heat and energetic carriers. Plasmonic nanostructures, which are able to harvest and convert the abundant sunlight to drive chemical reactions, have shown great prospects in heterogeneous photocatalysis. To maximize solar energy utilization, the rational design and precise manipulation of plasmonic nanostructures are, therefore, essential to obtain their strong light–matter interaction. In this review, we focus on the very recent advances in harnessing single-active plasmonic nanocatalysts (i.e., plasmonic materials as the only photo- and catalytic-active species), involving noble metals and doped-semiconductors, for enhanced photocatalytic reactions with visible light.

Design and functionalization of photocatalytic systems within mesoporous silica.

In the past decades, various photocatalysts such as TiO2, transition-metal-oxide moieties within cavities and frameworks, or metal complexes have attracted considerable attention in light-excited catalytic processes. Owing to high surface areas, transparency to UV and visible light as well as easily modified surfaces, mesoporous silica-based materials have been widely used as excellent hosts for designing efficient photocatalytic systems under the background of environmental remediation and solar-energy utilization. This Minireview mainly focuses on the surface-chemistry engineering of TiO2/mesoporous silica photocatalytic systems and fabrication of binary oxides and nanocatalysts in mesoporous single-site-photocatalyst frameworks. Recently, metallic nanostructures with localized surface plasmon resonance (LSPR) have been widely studied in catalytic applications harvesting light irradiation. Accordingly, silver and gold nanostructures confined in mesoporous silica and their corresponding catalytic activity enhanced by the LSPR effect will be introduced. In addition, the integration of metal complexes within mesoporous silica materials for the construction of functional inorganic-organic supramolecular photocatalysts will be briefly described.

A Plasmonic Molybdenum Oxide Hybrid with Reversible Tunability for Visible‐Light‐Enhanced Catalytic Reactions

A plasmonic hybrid having Pd nanoparticles on plasmonic MoO(3-x) is developed by a facile solution process, and its plasmonic resonance displays reversible tunability upon oxidation/reduction. Under visible-light irradiation, the Pd/MoO(3-x) hybrid exhibits plasmon-enhanced catalysis toward H2 evolution from ammonia borane hydrolysis and the Suzuki-Miyaura coupling reaction relative to dark conditions.

Enhanced Catalytic Activity on Titanosilicate Molecular Sieves Controlled by Cation−π Interactions

A new class of heterogeneous catalytic systems utilizing cation-guest interactions was designed based on microporous titanosilicate molecular sieves. Introducing heavier alkali metal cations on ion-exchange sites of the framework resulted in a significant enhancement of the catalytic activity for oxidation of cyclohexene and styrene, whereas such an enhancement was not observed in oxidation of cyclohexane without π systems. Distinct relationships between the catalytic activities and intermolecular interaction energies which were determined by IR spectroscopic and computational approaches clearly evidenced the predominance of the cation-π interaction in this catalytic system.