Search

This work presents the synthesis of Pd-loaded microporous titanosilicalite-1 (Pd/TS-1) and Pd-loaded hierarchical titanosilicalite-1 (Pd/HTS-1) with abundant mesopores (2-30 nm) inside the framework via hydrothermal method using polydiallydimethyl ammonium chloride as the non-surfactant mesopore template. XRD, N 2 sorption, FT-IR, FESEM-EDX, TEM, XPS, and DR-UV techniques were used to characterize the morphological and physicochemical properties of the synthesized materials. These materials were tested as heterogeneous catalysts, along with tetrapropylammonium bromide as co-catalyst, for cycloaddition reactions of CO 2 with epoxides to produce cyclic carbonates. It was found that the epoxide conversions were influenced by acidity and pore accessibility of the catalysts. Using Pd/HTS-1 facilitated bulky substrates to access active sites, resulting in higher conversions than Pd/TS-1. Over 85 % conversions were achieved for at least five consecutive cycles without significant loss in catalytic activity. The interaction between the Pd active surfaces and epichlorohydrin (ECH) was further studied by DFT calculations. The existence of Pd(200) was more influential on adsorbing epichlorohydrin (ECH) and subsequent formation of dissociated ECH (DECH) intermediate than Pd(111) surface. However, Pd(111) was dominant in enhancing the activity of DECH species for capturing CO 2 . Therefore, the co-existence of Pd(200) and Pd(111) surfaces was needed for cycloaddition of CO 2 with ECH., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Electrocatalytic and thermocatalytic CO 2 conversions provide promising routes to realize global carbon neutrality, and the development of corresponding advanced catalysts is important but challenging. Hollow-structured carbon (HSC) materials with striking features, including unique cavity structure, good permeability, large surface area, and readily functionalizable surface, are flexible platforms for designing high-performance catalysts. In this review, the topics range from the accurate design of HSC materials to specific electrocatalytic and thermocatalytic CO 2 conversion applications, aiming to address the drawbacks of conventional catalysts, such as sluggish reaction kinetics, inadequate selectivity, and poor stability. Firstly, the synthetic methods of HSC, including the hard template route, soft template approach, and self-template strategy are summarized, with an evaluation of their characteristics and applicability. Subsequently, the functionalization strategies (nonmetal doping, metal single-atom anchoring, and metal nanoparticle modification) for HSC are comprehensively discussed. Lastly, the recent achievements of intriguing HSC-based materials in electrocatalytic and thermocatalytic CO 2 conversion applications are presented, with a particular focus on revealing the relationship between catalyst structure and activity. We anticipate that the review can provide some ideas for designing highly active and durable catalytic systems for CO 2 valorization and beyond., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Hydrogenated molybdenum suboxide (H x MoO 3- y ) is a promising photothermal energy conversion (PEC) material. However, its charge carrier dynamics and underlying mechanisms remain unclear. Utilizing flash-photolysis time-resolved microwave conductivity, we investigated charge carrier-dielectric interactions in the Pt/H x MoO 3- y composite. The charge recombination of H 2 -reduced Pt/H x MoO 3- y was 2-3 orders of magnitude faster than that of Pt/MoO 3 , indicating efficient PEC. A complex photoconductivity study revealed that Pt/H x MoO 3- y has two types of trapping mechanisms, Drude-Zener (DZ) and negative permittivity effect (NPE) modes, depending on the reduction temperature. Pt/H x MoO 3- y reduced at 100 °C exhibited a dominant NPE owing to the electrical interaction of trapped charges with the surrounding ions and/or OH base. This polaronic trapped state retarded the PEC process. We found Pt/H x MoO 3- y reduced at 200 °C to be optimal owing to the balanced suppression of the NPE and charge diffusion. This is the first report revealing the charge dynamics in hydrogenated metal oxides and their impacts on PEC processes.

Al-MIL-101-NH 2 , which was previously regarded as being inactive as a photocatalyst, produces hydrogen peroxide (H 2 O 2 ) via O 2 reduction under visible-light irradiation, accompanied by efficient suppression of undesired H 2 O 2 decomposition. The low-coordination Lewis acid sites in trimetric Al-oxo clusters are crucial for the electron transfer to O 2 .

The localized surface plasmon resonance (LSPR) of noble metals has been investigated for decades for applications in various catalysis reactions and optical research studies, but its development has been hampered by inefficient light absorption and high costs. In comparison, the creation of less expensive semiconductors (metal oxides) with strong plasmonic absorption is an appealing option, particularly defective molybdenum oxide (H x MoO 3- y ) has received considerable attention and investigation as a promising plasmonic material for a variety of catalytic reactions (photocatalysis, thermocatalysis, photothermal catalysis, etc. ).The LSPR effect of H x MoO 3- y can be tuned throughout a broad spectrum range from visible to near-infrared (NIR) by altering the doping amount by electrochemical control, chemical reduction, or photochemical control. Notably, defects (oxygen vacancies) in H x MoO 3- y arise in conjunction with the LSPR effect, resulting in the formation of unique and useful active sites in a range of catalytic processes. In this review, we explore the formation mechanism of H x MoO 3- y with plasmonic features and discuss its applications in photocatalysis, thermocatalysis, and photothermal catalysis.

Fenton reaction has important implications in biology- and environment-related remediation. Hydroxyl radicals ( • OH) and hydroxide (OH - ) were formed by a reaction between Fe(II) and hydrogen peroxide (H 2 O 2 ). The acidic H 2 O 2 /Fe(II/III) redox-induced low H 2 O 2 utilization efficiency is the bottleneck of Fenton reaction. Electron paramagnetic resonance, surface-enhanced Raman scattering, and density functional theory calculation indicate that the unpaired electrons in the defects of carbon quantum dots (CQDs) and the carboxylic groups at the edge have a synergistic effect on CQDs Fenton-like catalysis. This leads to a 33-fold higher H 2 O 2 utilization efficiency in comparison with Fe(II)/H 2 O 2 Fenton reaction, and the pseudo-first-order reaction rate constant ( k obs ) increases 38-fold that of Fe(III)/H 2 O 2 under equivalent conditions. The replacement of acidic H 2 O 2 /Fe(II/III) redox with CQD-mediated Fe(II/III) redox improves the sluggish Fe(II) generation. Highly effective production of • OH in CQDs-Fe(III)/H 2 O 2 dramatically decreases the selectivity of toxic intermediate benzoquinone. The inorganic ions and dissolved organic matter (DOM) in real groundwater show negligible effects on the CQDs Fenton-like catalysis process. This work presents a process with a higher efficiency of utilization of H 2 O 2 in situ chemical oxidation (ISCO) to remove persistent organic pollutants.

Hydrogen spillover can assist the introduction of defects such as Ti 3+ and concomitant oxygen vacancies (V O ) in a TiO 2 crystal, thereby inducing a new level below the conduction band to improve the conductivity of photogenerated electrons and the visible light absorption property of TiO 2 . Meanwhile, crystal facet engineering offers a promising approach to achieve improved activity by influencing the recombination step of the photogenerated electrons and holes. In this study, with the aim of achieving enhanced visible light-driven photocatalytic activity, rutile TiO 2 nanorods with different aspect ratios were synthesized by crystal facet engineering, and Pt-deposited TiO 2- x nanorods (Pt/TNR) were then obtained via reduction treatment assisted by hydrogen spillover. The reduction treatment at 200 °C induced the formation of surface Ti 3+ exclusively, whereas surface Ti 3+ and V O were formed by performing the reduction at 600 °C. The Pt/TNR with a higher aspect ratio reduced at 200 °C exhibited the highest activity in photocatalytic H 2 production under visible light irradiation owing to the synergistic effect of the introduction of Ti 3+ defects and the spatial charge carrier separation induced by crystal facet engineering.

Defect engineering of metal oxides is a facile and promising strategy to improve their photocatalytic activity. In the present study, Pt/TiO 2- x was prepared by a reduction treatment assisted by hydrogen spillover to pure rutile, anatase, and brookite and was subsequently used for hydrogen production from an aqueous methanol solution. With increasing reduction temperature, the photocatalytic activity of the rutile Pt/TiO 2- x increased substantially, whereas the activity of anatase Pt/TiO 2- x decreased and that of brookite Pt/TiO 2- x was independent of the treatment temperature. Electron-spin resonance analysis revealed that rutile and brookite possess similar defect sites (Ti 3+ and concomitant oxygen vacancy) after the reduction at 600 °C, whereas different resonance signals were observed for anatase after the reduction at 600 °C. During the reduction process, electrons donated from spillover hydrogen migrate between the conduction band and the inherent midgap states. This research demonstrates that the depth of the inherent midgap states, depending on the crystal phases, influences the generation of defects, which play a key role in the photocatalytic performance of Pt/TiO 2- x .

Production of methanol from anthropogenic carbon dioxide (CO 2 ) is a promising chemical process that can alleviate both the environmental burden and the dependence on fossil fuels. In catalytic CO 2 hydrogenation to methanol, reduction of CO 2 to intermediate species is generally considered to be a crucial step. It is of great significance to design and develop advanced heterogeneous catalysts and to engineer the surface structures to promote CO 2 -to-methanol conversion. We herein report an oxygen-defective molybdenum sub-oxide coupled with Pt nanoparticles (Pt/H x MoO 3- y ) which affords high methanol yield with a methanol formation rate of 1.53 mmol g -cat -1 h -1 in liquid-phase CO 2 hydrogenation under relatively mild reaction conditions (total 4.0 MPa, 200 °C), outperforming other oxide-supported Pt catalysts in terms of both the yield and selectivity for methanol. Experiments and comprehensive analyses including in situ X-ray absorption fine structure (XAFS), in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and density functional theory (DFT) calculations reveal that both abundant surface oxygen vacancies (V O ) and the redox ability of Mo species in quasi-stable H x MoO 3- y confer the catalyst with enhanced adsorption and activation capability to subsequently transform CO 2 to methanol. Moreover, the Pt NPs act as H 2 dissociation sites to regenerate oxygen vacancies and as hydrogenation sites for the CO intermediate to finally afford methanol. Based on the experimental and computational studies, an oxygen-vacancy-mediated "reverse Mars-van Krevelen (M-vK)" mechanism is proposed. This study affords a new strategy for the design and development of an efficient heterogeneous catalyst for CO 2 conversion., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Loading of molecular catalyst on the surface of semiconductors is an attractive way to boost the water oxidation activity. As active sites, molecular water oxidation cocatalysts show increasing attraction and application possibility. In order to compare the advantages between molecular catalysts with non-noble and noble metals, the loading of the Fe(salen) and Ru(salen) as cocatalyst precursors on the surface of Ti-Fe 2 O 3 was investigated Quasi-Fe(salen) and Ru(salen) improved the photocurrent density by 1.5 and 1.7 times compared to that of the original Ti-Fe 2 O 3 photoanode, respectively. The quasi-Fe(salen) could improve the conductivity and reaction kinetics on the photoanode surface. By contrast, the notable advancements could be attributed to more reaction sites for quasi-Ru(salen) as cocatalysts. Thus, non-noble quasi-Fe(salen) is a promising cocatalyst to replace the noble metal salen, and further optimization can be expected with regard to the precise control of reaction sites., (© 2021 Wiley-VCH GmbH.)

Effects of morphology and exposed crystal planes of NiO x -decorated CeO 2 (NiCeO 2 ) nanostructured catalysts on activity during CO 2 methanation were examined, using nanorod (NR), nanocube (NC), and nanooctahedron (NO) structures. The NiCeO 2 nanorods (NiCeO 2 -NR) showed superior activity to NiCeO 2 -NC and NiCeO 2 -NO along with excellent selectivity for CH 4 . This material also demonstrated exceptional durability, with no significant loss of catalytic activity or structural change after use. Comprehensive physicochemical characterization as well as density functional theory calculations determined that the high performance of the NiCeO 2 -NR was closely related to the large quantity of surface oxygen vacancies and the high degree of reversibility associated with the Ce 4+ ↔ Ce 3+ redox cycle of the support. These effects originate from the enhanced reactivity of oxygen atoms on the (110) surfaces of the oxide compared with the (100) and (111) surfaces. This information is expected to assist in the rational design of practical catalysts for the activation of CO 2 molecules and other important transformations.

Biodiesel is of high interest due to increased demand for energy with the concern regarding more sustainable production processes. However, an inevitable by-product is glycerol. Hence, the conversion of this by-product to higher-value chemicals, especially 1,3-propanediol (1,3-PDO) via glycerol hydrogenolysis reaction, is one of the most effective pathways towards a profitable process. In general, this process is catalyzed by a highly active Pt-based catalyst supported on γ-Al 2 O 3 . However, its low 1,3-PDO selectivity and stability due to surface deactivation of such catalysts remained. This led to the surface modification by WO x to improve both the selectivity by means of the increased Brønsted acidity and the stability in terms of Pt leaching-resistance. Hence, we applied experimental and density functional theory (DFT)-based techniques to study the fundamentals of how WO x modified the catalytic performance in the Pt/γ-Al 2 O 3 catalyst and provided design guidelines. The effects of WO x promoter on improved activity were due to the shifting of the total density of states towards the antibonding region evident by the total density of states (TDOS) profile. On the improved 1,3-PDO selectivity, the main reason was the increasing number of Brønsted acid sites due to the added WO x promoter. Interestingly, the stability improvement was due to the strong metal-support interaction (SMSI) that occurred in the catalyst, like typical high leaching-resistant catalysts. Also, the observed strong metal-support-promoter interaction (SMSPI) is an additional effect preventing leaching. The SMSPI stemmed from additional bonding between the WO x species and the Pt active site, which significantly strengthened Pt adsorption to support and a high electron transfer from both Pt and Al 2 O 3 to WO x promoter. This suggested that the promising promoter for our reaction performed in the liquid phase would improve the stability if SMSI occurred, where the special case of the WO x promoter would even highly improve the stability through SMSPI. Nevertheless, various promoters that can promote SMSPI need investigations.

As an environmentally friendly and renewable energy source, hydrogen peroxide (H2O2) could be produced photocatalytically through selective two-electron reduction of O2 using effective photocatalysts. Metal organic frameworks (MOFs), as hybrid porous materials consisting of organic linkers and metal oxide clusters, have aroused great interest in the design of effective catalysts for photocatalysis under visible light irradiation due to their unique properties, such as large surface area, good chemical stability, and diverse and tunable chemical components. In this perspective, we highlight our recent progress in the application of various MOF-based nanomaterials for photocatalytic H2O2 production from the selective two-electron reduction of O2 in a single-phase system (acetonitrile) and two-phase system (water/benzyl alcohol). Photocatalytic H2O2 production in the single-phase system achieved a higher activity using NiO as a cocatalyst of the MOF rather than Pt. Photocatalytic H2O2 production in the two-phase system using various hydrophobic MOFs showed further improved activity compared to the single-phase system. It has been possible to design a hydrophobic MOF-based photocatalyst with high activity and stability under recycling conditions. These studies gathered in this perspective revealed the novel application of MOFs in the field of energy production.

Nanoporous silica solids can offer opportunities for hosting photocatalytic components such as various tetra-coordinated transition metal ions to form systems referred to as "single-site photocatalysts". Under UV/visible-light irradiation, they form charge transfer excited states, which exhibit a localized charge separation and thus behave differently from those of bulk semiconductor photocatalysts exemplified by TiO 2 . This account presents an overview of the design of advanced functional materials based on the unique photo-excited mechanisms of single-site photocatalysts. Firstly, the incorporation of single-site photocatalysts within transparent porous silica films will be introduced, which exhibit not only unique photocatalytic properties, but also high surface hydrophilicity with self-cleaning and antifogging applications. Secondary, photo-assisted deposition (PAD) of metal precursors on single-site photocatalysts opens up a new route to prepare nanoparticles. Thirdly, visible light sensitive photocatalysts with single and/or binary oxides moieties can be prepared so as to use solar light, the ideal energy source., (© 2019 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Catalytic diesel soot combustion was examined using a series of Mn 2 O 3 catalysts with different morphologies, including plate, prism, hollow spheres and powders. The plate-shaped Mn 2 O 3 (Mn 2 O 3 -plate) exhibited superior carbon soot combustion activity compared to the prism-shaped, hollow-structured and powdery Mn 2 O 3 under both tight and loose contact modes at soot combustion temperatures (T 50 ) of 327 °C and 457 °C, respectively. Comprehensive characterization studies using scanning electron microscopy, scanning transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction and oxygen release measurements, revealed that the improved activity of Mn 2 O 3 -plate was mainly attributed to the high oxygen release rate of surface-adsorbed active oxygen species, which originated from oxygen vacancy sites introduced during the catalyst preparation, rather than specific surface-exposed planes. The study provides new insights for the design and synthesis of efficient oxidation catalysts for carbon soot combustion as well as for other oxidation reactions of harmful hydrocarbon compounds., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

MoS2 has been investigated as a low-cost alternative to Pt in the electrochemical hydrogen evolution reaction. One of the promising methods to further activate MoS2 is phase engineering. MoS2 generally exhibits two kinds of crystalline phases: hexagonal 2H phase and octahedral 1T phase. 1T-MoS2 exhibits much better chemical/physical properties than natural semiconductor 2H-MoS2. However, 1T-MoS2 is metastable and its synthesis is still a challenge. Hybrid 1T/2H-MoS2 has been synthesized under relatively mild conditions, but controlling the 1T/2H ratio is still an issue which has not been discussed in detail. In this study, the synthesis methods of hybrid phase 1T/2H-MoS2 with controllable 1T concentration are investigated. The electrochemical hydrogen evolution reaction is then evaluated for 1T/2H-MoS2 with different 1T concentrations by performing both experiments and theoretical calculations.

The development of advanced materials for heterogeneous catalytic applications requires fine control over the synthesis and structural parameters of the active site. Mesoporous silica materials have attracted increasing attention to be considered as an important class of nanostructured support materials in heterogeneous catalysis. Their large surface area, well-defined porous architecture and ability to incorporate metal atoms within the mesopores lead them to be a promising support material for designing a variety of different catalysts. In particular, SBA-15 mesoporous silica has its broad applicability in catalysis because of its comparatively thicker walls leading to higher thermal and mechanical stability. In this review article, various strategies to functionalize SBA-15 mesoporous silica have been reviewed with a view to evaluating its efficacy in different catalytic transformation reactions. Special attention has been given to the molecular engineering of the silica surface, within the framework and within the hexagonal mesoporous channels for anchoring metal oxides, single-site species and metal nanoparticles (NPs) serving as catalytically active sites.

This work demonstrated the use of TiO 2 as a promising platform for the synthesis of non-equilibrium RhCu binary alloy nanoparticles (NPs). These metals are regarded as immiscible based on their phase diagram but form NPs with the aid of the significant hydrogen spillover on TiO 2 with concurrent proton-electron transfer. The resulting RhCu/TiO 2 exhibited 2.6 times higher catalytic activity than Rh/TiO 2 during hydrogen production from the hydrolysis of ammonia borane (AB), due to a synergistic effect. Theoretical simulations showed a higher energy value for the adsorption of AB on the RhCu alloy and a lower activation energy for the rate determining N-B bond dissociation by the attack of H 2 O during AB hydrolysis compared to monometallic Rh. High-angle annular dark-field scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy confirmed the formation of RhCu alloy NPs with a mean diameter of 2.0 nm on the TiO 2 . H 2 -temperature programmed reduction and in situ X-ray absorption fine structure analyses at elevated temperature under H 2 demonstrated that Rh 3+ and Cu 2+ precursors were simultaneously reduced only on the TiO 2 support. This effect resulted from the improved and limited reducibility of Cu 2+ and Rh 3+ , respectively. The rate of hydrogen spillover of TiO 2 is faster as compared to γ-Al 2 O 3 and MgO as evidenced by sequential H 2 /D 2 exchanges during in situ Fourier transform infrared analyses. Density functional theory calculations also showed that the migration of H atoms on TiO 2 proceeds with a lower energy barrier than that on Al 2 O 3 , and the reduction of Cu 2+ species is facilitated by H spillover on the support rather than by direct reduction by H 2 . These results confirm the vital role of TiO 2 in the formation of the alloy and may represent a new strategy for the synthesis of different non-equilibrium solid solution alloys., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Phase engineering has been recognized as a promising method for boosting the catalytic activity of molybdenum sulfide (MoS 2 ) in the field of electrocatalysts and photocatalysts. The metallic 1T-MoS 2 exhibits much higher catalytic activity than natural semiconducting 2H-MoS 2 but suffers from harsh synthetic conditions and metastable physical/chemical properties. The hybrid 1T/2H phase MoS 2 shows higher catalytic activity than the 2H-MoS 2 and exhibits better stability than the 1T-MoS 2 , which is more favorable than the 2H-MoS 2 in the photocatalytic reactions. In this study, we report a hydrothermal synthesis of the hybrid 1T/2H-MoS 2 phase coupled with SiC as a heterojunction photocatalyst for 4-nitrophenol (4-NP) degradation. SiC acts as a counterpart of the heterojunction structure and a morphology modifier, which dramatically promotes the reaction rate and visible light responsibility, providing new candidates and strategies in photocatalysis.

The effect of the morphology, which exposes different crystal planes, on the physicochemical properties and catalytic activity in diesel carbon soot oxidation was studied using CoOx-decorated CeO2 (CoCeO2) heterostructured catalysts, such as nanorods (NRs), nanocubes (NCs), and nanoparticles (NPs). The CoOx/CeO2 nanorods (CoCeO2-NR) showed superior carbon soot combustion activity at lower temperatures to CoCeO2-NCs and CoCeO2-NPs under both tight and loose contact modes with soot combustion temperatures (T50) of 321 and 494 °C, respectively. A comprehensive analysis by means of X-ray diffraction, Raman spectroscopy, high-angle annular dark-field scanning transmission electron microscopy, in situ X-ray absorption fine structure, temperature-programmed reduction, oxygen storage/release measurements, and density functional theory calculations revealed that the improved activity of CoCeO2-NRs is mainly ascribed to the high oxygen release rate and strong redox capability of the supported Co species, with complete reversibility. This originates from the high reactivity of oxygen atoms on (110) surfaces, compared to (100) and (111) surfaces over CeO2. Additionally, CoCeO2-NRs displayed durability and recyclability without any significant loss of catalytic activity or structural change. These insights will aid in the rational design of practical catalysts for the purification of diesel exhaust and other important transformations.

Formic acid (FA; HCOOH) is one of the most promising candidates for the storage of hydrogen (H 2 ). Herein, we report a H 2 storage/production system based on the hydrogenation of CO 2 and dehydrogenation of FA, using a nanostructured heterogeneous catalyst. Pd 1 Ag 2 nanoparticles with an average size of 2.8 nm were encapsulated within a zeolitic imidazolate framework (ZIF-8) having a core-shell structure (ZIF-8@Pd 1 Ag 2 @ZIF-8). This composite displayed high activity and stability during both the hydrogenation of CO 2 to produce FA and the dehydrogenation of FA into H 2 and CO 2 . This improved performance is attributed to the use of ultrafine Pd 1 Ag 2 nanoparticles as well as the spatial regulation of the nanoparticles within the reaction field. This study suggests a new strategy for controlling the spatial distribution of metal nanoparticles within MOFs so as to fine-tune the catalytic activity and selectivity of ZIF-8@metal nanoparticles@ZIF-8 catalysts.

A new type of pyrene-thiol derivative-modified Pd nanoparticle (NP) catalyst on a carbon black support for the efficient semihydrogenation of alkynes to alkenes is reported herein. Colloidal Pd NPs surrounded by pyrene-thiol modifiers were prepared using the two-phase Brust method followed by impregnation of carbon black materials. Based on the structural characterization of the prepared catalyst (PyC 12 S-Pd/VC) by NMR, UV-vis, FT-IR, TEM, HAADF-STEM, Pd K-edge XAFS, XRD, N 2 adsorption, and XPS, we show that highly dispersed Pd NPs are immobilized on the catalysts via π-π interaction between pyrene groups bound to the Pd NPs and carbon black supports. PyC 12 S-Pd/VC efficiently catalyzes the alkyne semihydrogenation reaction while maintaining high alkene selectivity; an alkene selectivity of 94% is attained at 98% conversion after 5 h of reaction, and the selectivity was retained around 80% in 10 h of reaction. This performance is superior to that of a catalyst without pyrene groups and that of a commercial Lindlar catalyst. The steric hindrance of pyrene groups restricts access of the substrates to Pd NP surfaces, suppressing the unfavorable overhydrogenation of alkenes to alkanes, which is revealed by the solvent and substrate dependency on the catalytic performance and a DFT calculation study. Furthermore, the high selectivity and stability of PyC 12 S-Pd/VC are caused by the strong interaction between pyrene groups and carbon supports, which prevents the separation of pyrene modifiers and the leaching or sintering of Pd NPs during the catalytic reaction. It is demonstrated that the combination of Pd NPs, pyrene-thiol modifiers, and carbon supports offers high activity, alkene selectivity, and stability in the semihydrogenation reaction.

The photocatalytic dehydrogenation of formic acid has recently emerged as an outstanding alternative to the traditional thermal catalysts widely applied in this reaction. The utilization of photocatalytic processes for the production of hydrogen is an appealing strategy that perfectly matches with the idea of a green and sustainable future energy scenario. However, it sounds easier than it is, and great efforts have been needed to design and develop highly efficient photocatalysts for the production of hydrogen from formic acid. In this work, some of the most representative strategies adopted for this application are reviewed, paying particular attention to systems based on TiO 2 , CdS and C 3 N 4 .

A hydrophobic MOF, OPA/MIL-125-NH2, whose Ti cluster was alkylated with octadecylphosphonic acid (OPA), was found to enhance photocatalytic H2O2 production in a two-phase system. Its activity exceeded that of linker-alkylated MIL-125-NH2. OPA/MIL-125-NH2 was modified on its outermost surface, which resulted in the activity enhancement while preserving the inner pores of the inherent MOF.

Much effort has been devoted to photocatalytic production of hydrogen peroxide (H 2 O 2 ) as an alternative to fossil fuels. From an economic point of view, reductive synthesis of H 2 O 2 from O 2 coupled with the oxidative synthesis of value-added products is particularly interesting. We herein report application of MIL-125-NH 2 , a photoactive metal-organic framework (MOF), to a benzylalcohol/water two-phase system that realized photocatalytic production and spontaneous separation of H 2 O 2 and benzaldehyde. Hydrophobization of the MOF enabled its separation from the aqueous phase. This resulted in enhanced photocatalytic efficiency and enabled application of various aqueous solutions including extremely low pH solution which is favorable for H 2 O 2 production but fatal to MOF structure. In addition, a highly concentrated H 2 O 2 solution was obtained by simply reducing the volume of the aqueous phase., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Molybdenum disulfide (MoS 2 ) has been regarded as a favorable photocatalytic co-catalyst and efficient hydrogen evolution reaction (HER) electrocatalyst alternative to expensive noble-metals catalysts, owing to earth-abundance, proper band gap, high surface area, and fast electron transfer ability. In order to achieve a higher catalytic efficiency, defects strategies such as phase engineering and vacancy introduction are considered as promising methods for natural 2H-MoS 2 to increase its active sites and promote electron transfer rate. In this study, we report a new two-step defect engineering process to generate vacancies-rich hybrid-phase MoS 2 and to introduce Ru particles at the same time, which includes hydrothermal reaction and a subsequent hydrogen reduction. Compositional and structural properties of the synthesized defects-rich MoS 2 are investigated by XRD, XPS, XAFS and Raman measurements, and the electrochemical hydrogen evolution reaction performance, as well as photocatalytic hydrogen evolution performance in the ammonia borane dehydrogenation are evaluated. Both catalytic activities are boosted with the increase of defects concentrations in MoS 2 , which ascertains that the defects engineering is a promising route to promote catalytic performance of MoS 2 ., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Silica-based micro-, meso-, macro-porous materials offer attractive routes for designing single-site photocatalysts, supporting semiconducting nanoparticles, anchoring light-responsive metal complexes, and encapsulating metal nanoparticles to drive photochemical reactions by taking advantage of their large surface area, controllable pore channels, remarkable transparency to UV/vis and tailorable physicochemical surface characteristics. This review mainly focuses on the fascinating photocatalytic properties of silica-supported Ti catalysts from single-site catalysts to nanoparticles, their surface-chemistry engineering, such as the hydrophobic modification and synthesis of thin films, and the fabrication of nanocatalysts including morphology controlled plasmonic nanostructures with localized surface plasmon resonance. The hybridization of visible-light responsive metal complexes with porous materials for the construction of functional inorganic-organic supramolecular photocatalysts is also included. In addition, the latest progress in the application of MOFs as excellent hosts for designing photocatalytic systems is described.

Photocatalytic H2O2 production via two-electron reduction of O2 was realized by visible-light irradiation of a metal-organic framework, MIL-125-NH2, in the presence of TEOA and benzylalcohol. Deposition of NiO nanoparticles onto MIL-125-NH2 dramatically enhanced the catalytic activity. Further studies suggested that fast disproportionation of the O2˙- intermediate to H2O2 resulted in the enhancement.

Harvesting solar light to boost commercially important organic synthesis still remains a challenge. Coupling of conventional noble metal catalysts with plasmonic oxide materials which exhibit intense plasmon absorption in the visible light region is a promising option for efficient solar energy utilization in catalysis. Herein, we for the first time demonstrate that plasmonic hydrogen molybdenum bronze coupled with Pt nanoparticles (Pt/H x MoO 3- y ) shows a high catalytic performance in the deoxygenation of sulfoxides with 1 atm of H 2 at room temperature, with dramatic activity enhancement under visible light irradiation relative to dark conditions. The plasmonic molybdenum oxide hybrids with strong plasmon resonance peaks pinning at around 556 nm are obtained via a facile H-spillover process. Pt/H x MoO 3- y hybrid provides excellent selectivity for the deoxygenation of various sulfoxides as well as pyridine N-oxides, in which drastically improved catalytic efficiencies are obtained under the irradiation of visible light. Comprehensive analyses reveal that oxygen vacancies massively introduced via a H-spillover process are the main active sites, and the reversible redox property of Mo atoms and strong plasmonic absorption play key roles in this reaction. The catalytic system works under extremely mild conditions and can boost the reaction by the assistance of visible light, offering an ultimately greener protocol to produce sulfides from sulfoxides. Our findings may open up a new strategy for designing plasmon-based catalytic systems that can harness visible light efficiently.

Single-site photocatalysts generally display excellent photocatalytic activity and considerably high stability compared with homogeneous catalytic systems. A rational structural design of single-site photocatalysts with isolated, uniform, and spatially separated active sites in a given solid is of prime importance to achieve high photocatalytic activity. Intense attention has been focused on the design and fabrication of single-site photocatalysts by using porous materials as a platform. Metal-organic frameworks (MOFs) have great potential in the design and fabrication of single-site photocatalysts due to their remarkable porosity, ultrahigh surface area, extraordinary tailorability, and significant diversity. MOFs can provide an abundant number of binding sites to anchor active sites, which results in a significant enhancement in photocatalytic performance. In this focus review, the development of single-site MOF photocatalysts that perform important and challenging chemical redox reactions, such as photocatalytic H 2 production, photocatalytic CO 2 conversion, and organic transformations, is summarized thoroughly. Successful strategies for the construction of single-site MOF photocatalysts are summarized and major challenges in their practical applications are noted., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Metal organic frameworks (MOFs) are a class of porous organic-inorganic crystalline materials that have attracted much attention as H 2 storage devices and catalytic supports. In this paper, the synthesis of highly-dispersed Ni nanoparticles (NPs) for the hydrogenation of olefins was achieved by employing Ni-MOF-74 as a precursor. Investigations of the structural transformation of Ni species derived from Ni-MOF-74 during heat treatment were conducted. The transformation was monitored in detail by a combination of XRD, in situ XAFS, and XPS measurements. Ni NPs prepared from Ni-MOF-74 were easily reduced by the generation of reducing gases accompanied by the decomposition of Ni-MOF-74 structures during heat treatment at over 300 °C under N 2 flow. Ni-MOF-74-300 exhibited the highest activity for the hydrogenation of 1-octene due to efficient suppression of excess agglomerated Ni species during heat treatment. Moreover, Ni-MOF-74-300 showed not only high activity for the hydrogenation of olefins but also high size-selectivity because of the selective formation of Ni NPs covered by MOFs and the MOF-derived carbonaceous layer., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Liquid-phase oxidation of alkylaromatics with molecular O 2 was examined using a microporous Mn-based metal-organic framework (Mn-MOF-74). Mn-MOF-74 consisting of trimeric Mn clusters and 2,5-dihydroxyterephthalate (dhtp) linkers exhibits superior catalytic activity with good ketone selectivity compared to conventional oxide-supported Mn catalysts without showing any lengthy induction period. Combined analyses by means of XRD, FE-SEM, N 2 physisorption and Mn K-edge XAFS reveal that the superior catalytic performance is attributed to the inherently-formed Mn(iii) 2 (dhtp) moieties embedded in the Mn-MOF-74 framework rather than structural factors associated with the MOF. The catalyst is reusable over multiple catalytic runs along with retaining its original catalytic activity due to the ability of the dhtp ligand to stabilize active Mn(iii) atoms. Owing to high activity, reusability and nontoxicity, Mn-MOF-74 can offer a simple, inexpensive and efficient protocol for the oxidation of some important alkylaromatics, such as ethylbenzene and diphenylmethane to produce the corresponding aromatic ketones.

Yolk-shell nanostructured photocatalyst which consists of inner core photocatalytic particles and outer silica shell exhibits high photocatalytic efficiency and molecular size selectivity due to the molecular sieving property of the outer shell. Creation of extended porosity in the shell endows it with improved adsorption properties and size selectivity toward targeted reactants. In this study, yolk-shell nanostructured photocatalyst consisting of TiO 2 NPs core and porous silica shell with controllable pore size was fabricated through a facile single-step dual-templating approach utilizing oil-in-water (O/W) microemulsions and amphiphilic protein molecules. Addition of optimum amount of protein (ovalbumin) as a sacrificial template together with O/W microemulsion during the synthesis led to the expansion of average pore size from 2.0 to 3.6 nm, while retaining TiO 2 -encapsulated yolk-shell nanostructures. Photocatalytic degradation tests using gaseous 2-propanol and huge proteins as model substrates clearly revealed that the obtained material (TiO 2 @HSS_pro) showed superior photocatalytic performances with both improved photocatalytic efficiency and molecular size selectivity due to the increased surface area and expanded pore diameter.

Pd nanoparticles (NPs) supported on Ti-doped graphitic carbon nitride (g-C 3 N 4 ) were synthesized by a deposition-precipitation route and a subsequent reduction with NaBH 4 . The features of the NPs were studied by XRD, TEM, FTIR, XPS, EXAFS and N 2 -physisorption measurements. It was found that the NPs had an average size of 2.9 nm and presented a high dispersion on the surface of Ti-doped g-C 3 N 4 . Compared to Pd loaded on pristine g-C 3 N 4 , the Pd NPs supported on Ti-doped g-C 3 N 4 exhibited a high catalytic activity in formic acid dehydrogenation in water at room temperature. The enhanced activity could be attributed to the small Pd NPs size, as well as the strong interaction between Pd NPs and Ti-doped g-C 3 N 4 ., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Ag nanoparticles (NPs) have gained great attention owing to their interesting plasmonic properties and efficient catalysis under visible-light irradiation. In this study, an Ag-based plasmonic catalyst supported on mesoporous silica with isolated and tetrahedrally coordinated single-site Ti-oxide moieties, namely, Ag/Ti-SBA-15, was designed with the purpose of utilizing the broad spectral range of solar energy. The Ti-SBA-15 support allows the deposition of small Ag NPs with a narrow size distribution. The chemical structure, morphology, and optical properties of the prepared catalyst were characterized by techniques such as UV/Vis, FT extended X-ray absorption fine structure, and X-ray photoelectron spectroscopy, field-emission SEM, TEM, and N 2 physisorption studies. The catalytic activity of Ag/Ti-SBA-15 in hydrogen production from ammonia borane by hydrolysis was significantly enhanced in comparison with Ag/SBA-15 without Ti-oxide moieties and Ag/TiO 2 /SBA-15 involving agglomerated TiO 2 , both in the dark and under light irradiation. Improved electron transfer under light irradiation caused by the creation of heterojunctions between Ag NPs and Ti-oxide moieties explains the results obtained in the present study., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Realizing accurate control of catalytically active centers on solid surfaces is one of the most essential goals in the development of functionalized heterogeneous catalysts. Controlled synthesis of carbon-supported Co catalysts from single-site to nanoparticles can be successfully achieved by the structural transformation of the deposited Co(salen) complex precursor under heat treatment. The obtained structures were characterized using techniques such as XRD, in situ XAFS, and TEM. The first decomposition of the Co(salen) complex is initiated by the dissociation of Co-O-C bonds at around 250 °C, which produces isolated single-atom Co species while retaining the Co-N-C bonds even up to 400 °C. When the heat treatment temperature exceeds 450 °C, the second decomposition of the Co-N-C bonds occurs to form Co oxide nanoclusters followed by the growth of Co NPs upon further increase of the heat treatment temperature. The single-site catalyst is highly dispersed and electronically deficient owing to the interaction with the carbon support, and shows activity and selectivity for the oxidation of ethylbenzene, as compared to the inherent Co(salen) complex and nanoparticle catalysts.

TiO 2 nanoparticles (NPs) encapsulated in hollow silica spheres (TiO 2 @HSSs) show a shielding-effect that can insulate photocatalytically active TiO 2 NPs from the surrounding environment and thus prohibit the self-degradation of organic support materials under ultraviolet (UV)-light irradiation. In this study, photocatalytically active papers were fabricated by combining TiO 2 @HSS and cellulose fibers, and their photocatalytic activities and durability under UV-light irradiation were examined. The yolk-shell nanostructured TiO 2 @HSS, which has an ample void space between inner TiO 2 NPs and an outer silica shell, was synthesized using a facile single-step method utilizing an oil-in-water microemulsion as an organic template. The thus-prepared TiO 2 @HSS particles were deposited onto a cellulose paper either by the chemical adhesion process via ionic bonding or by the physical adhesion process using a dual polymer system. The obtained paper containing TiO 2 @HSS particles with high air permeability exhibited a higher photocatalytic activity in the photocatalytic decomposition of volatile organic compounds than unsupported powdery TiO 2 @HSS particles because of the uniform dispersion on the paper with a reticular fiber network. In addition, the paper was hardly damaged under UV-light irradiation, whereas the paper containing naked TiO 2 NPs showed a marked deterioration with a considerably decreased strength, owing to the ability of the silica shell to prevent direct contact between TiO 2 and organic fibers. This study can offer a promising method to fabricate photocatalytically active papers with a photoresistance property available for real air cleaning.

One-pot reaction involving Pd-catalyzed H 2 O 2 production from H 2 and O 2 and Ti-catalyzed successive oxidation with H 2 O 2 in a single reaction vessel is an alluring strategy for the synthesis of targeted chemicals in terms of sustainability and economic competitiveness. In this study, a yolk-shell nanostructured catalyst, consisting of Pd nanoparticles (NPs) with core diameter ca. 4.0 nm and a porous titanosilicate shell of ca. 15 nm thickness, was fabricated by using an oil-in-water (O/W) microemulsion-based interfacial self-assembly approach. Compared with prototype titanosilicate-supported Pd NP catalysts and core-shell structured analogues, the yolk-shell nanostructured catalyst exhibited superior catalytic efficiency in the one-pot oxidation reaction of sulfides with 83 % H 2 O 2 utilization efficiency, because of the productive effect of the titanosilicate shell in limiting the diffusion of H 2 O 2 generated in situ over the encapsulated Pd NPs and the efficient access of the H 2 O 2 to the neighboring active Ti sites. This study provides promising avenues for the development of multifunctional nanostructured catalysts that are useful for one-pot reactions., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Palladium nanoparticles (Pd NPs) were synthesized by the reduction-by-solvent method using polyvinylpirrolidone (PVP) as capping agent. The nonstatic interaction between PVP and the metallic surface may change the properties of the NPs due to the different possible interactions, through either the O or N atoms of the PVP. In order to analyze these effects and their repercussions in their catalytic performance, Pd NPs with various PVP/Pd molar ratios (1, 10, and 20) were prepared, deposited on silica, and tested in the formic acid decomposition reaction. The catalytic tests were conducted using catalysts prepared by loading NPs with three different time lapses between their purification and their deposition on the silica support (1 day, 1 month, and 6 months). CO adsorption, FTIR spectroscopy, XPS, and TEM characterization were used to determine the accessibility of the Pd NPs surface sites, the electronic state of Pd, and the average NPs size, respectively. The H 2 production from the formic acid decomposition reaction has a strong dependence on the Pd surface features, which in turn are related to the NPs aging time due to the progressive removal of the PVP.

A straightforward aqueous synthesis of MoO3-x nanoparticles at room temperature was developed by using (NH4 )6 Mo7 O24 ⋅4 H2 O and MoCl5 as precursors in the absence of reductants, inert gas, and organic solvents. SEM and TEM images indicate the as-prepared products are nanoparticles with diameters of 90-180 nm. The diffuse reflectance UV-visible-near-IR spectra of the samples indicate localized surface plasmon resonance (LSPR) properties generated by the introduction of oxygen vacancies. Owing to its strong plasmonic absorption in the visible-light and near-infrared region, such nanostructures exhibit an enhancement of activity toward visible-light catalytic hydrogen generation. MoO3-x nanoparticles synthesized with a molar ratio of Mo(VI) /Mo(V) 1:1 show the highest yield of H2 evolution. The cycling catalytic performance has been investigated to indicate the structural and chemical stability of the as-prepared plasmonic MoO3-x nanoparticles, which reveals its potential application in visible-light catalytic hydrogen production., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In this work, we propose a straightforward method to enhance the catalytic activity of AB dehydrogenation by using non-noble-metal nanoparticle supported on chromium-based metal-organic framework (MIL-101). It was demonstrated to be effective for hydrogen generation from ammonia borane under assistance of visible light irradiation as a noble-metal-free catalyst. The catalytic activity of metal nanoparticles supported on MIL-101 under visible light irradiation is remarkably higher than that without light irradiation. The TOFs of Cu/MIL-101, Co/MIL-101, and Ni/MIL-101 are 1693, 1571, and 3238 h(-1), respectively. The enhanced activity of catalysts can be primarily attributed to the cooperative promoting effects from both non-noble-metal nanoparticles and photoactive metal-organic framework in activating the ammonia borane molecule and strong ability in the photocatalytic production of hydroxyl radicals, superoxide anions, and electron-rich non-noble-metal nanoparticle. This work sheds light on the exploration of active non-noble metals supported on photoactive porous materials for achieving high catalytic activity of various redox reactions under visible light irradiation.

The shape and composition effects of platinum-palladium (Pt-Pd) alloy nanoparticle cocatalysts on visible-light photocatalytic hydrogen evolution from an aqueous ammonium sulphite solution have been reported and discussed. The activity of Pt-Pd nanoparticles loaded Pt-Pd/CdS photocatalysts are affected based on both the Pt-Pd alloy nanoparticles' shape and their compositions. In this research, two shapes of Pt-Pd nanoparticles have been studied. One is Pt-Pd nanocubes enclosed by {100} crystal planes and the other is nano-octahedra covered with {111} crystal facets. Results show that the photocatalytic turnover frequency (TOF), defined as moles of hydrogen produced per surface mole of Pt-Pd metal atom per second, for Pt-Pd nanocubes/CdS (Pt-Pd NCs/CdS) photocatalyst can be 3.4 times more effective than Pt-Pd nano-octahedra/CdS (Pt-Pd NOTa/CdS) nanocomposite photocatalyst. Along with the shape effect, the atomic ratio of Pt to Pd can also impact the efficiency of Pt-Pd/CdS photocatalysts. When the Pt to Pd atomic ratio changes from 1:0 to about 2:1, the rate of hydrogen production increases from 900 μmol/h for Pt NCs/CdS catalyst to 1837 μmol/h for Pt-Pd (2:1) NCs/CdS photocatalyst-a 104% rate increase. This result suggests that the 33 mol % of more expensive Pt can be replaced with less costly Pd, resulting in a more than 100% hydrogen production rate increase. The finding of this research will lead to the research and development of highly effective catalysts for photocatalytic hydrogen production using solar photonic energy.

Heavily doped semiconductors have recently emerged as a remarkable class of plasmonic alternative to conventional noble metals; however, controlled manipulation of their surface plasmon bands toward short wavelengths, especially in the visible light spectrum, still remains a challenge. Here we demonstrate that hydrogen doped given MoO3 and WO3 via a facile H-spillover approach, namely, hydrogen bronzes, exhibit strong localized surface plasmon resonances in the visible light region. Through variation of their stoichiometric compositions, tunable plasmon resonances could be observed in a wide range, which hinge upon the reduction temperatures, metal species, the nature and the size of metal oxide supports in the synthetic H2 reduction process as well as oxidation treatment in the postsynthetic process. Density functional theory calculations unravel that the intercalation of hydrogen atoms into the given host structures yields appreciable delocalized electrons, enabling their plasmonic properties. The plasmonic hybrids show potentials in heterogeneous catalysis, in which visible light irradiation enhanced catalytic performance toward p-nitrophenol reduction relative to dark condition. Our findings provide direct evidence for achieving plasmon resonances in hydrogen doped metal oxide semiconductors, and may allow large-scale applications with low-price and earth-abundant elements.

A microwave-antenna strategy was developed for the in situ synthesis of Cu nanowire (CuNW) threaded ZIF-8. The CuNWs acted as microwave-antennas to generate surface "super hot" dots. The high temperature of "super hot" dots induced adsorption and coordination of metal ions and organic ligands, followed by in situ assembly and crystal-growth along the CuNWs. This catalyst exhibited high activity and stability in H2 production via NH3BH3 hydrolysis owing to the synergetic effect. The CuNWs supplied a rapid electron transfer channel while ZIF-8 assembled on the CuNWs offered a large capacity for adsorbing reactants and channels for rapidly transferring H(-)/H(+) ions toward Cu active sites. Other one-dimensional threaded MOFs, including CuNW threaded MOF-5 and UIO-66, or carbon nanotube threaded ZIF-8 and ZIF-67 could also be prepared using the microwave-antenna strategy.

Skeletal Ni catalysts were prepared from Ni-Zr alloys, which possess different chemical composition and atomic arrangements, by a combination of thermal treatment and treatment with aqueous HF. Hydrogen generation from ammonia borane over the skeletal Ni catalysts proceeded efficiently, whereas the amorphous Ni-Zr alloy was inactive. Skeletal Ni prepared from amorphous Ni30 Zr70 alloy had a higher catalytic activity than that prepared from amorphous Ni40 Zr60 and Ni50 Zr50 alloys. The atomic arrangement of the Ni-Zr alloy also strongly affected the surface structure and catalytic activities. Thermal treatment of the amorphous Ni-Zr alloys at a temperature slightly lower than the crystallization temperature led to an increase of the number of surface-exposed Ni atoms and an enhancement of the catalytic activities for hydrogen generation from ammonia borane. The skeletal Ni catalysts also showed excellent durability and recyclability., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Metal-support interactions (MSIs) and particle size play important roles in catalytic reactions. For the first time, silver nanoparticles supported on CeO2-SBA-15 supports are reported that possess tunable particle size and MSIs, as prepared by microwave (MW) irradiation, owing to strong charge polarization of CeO2 clusters (i.e., MW absorption). Characterizations, including TEM, X-ray photoelectron spectroscopy, and extended X-ray absorption fine structure, were carried out to disclose the influence of CeO2 contents on the Ag particle size, MSI effect between Ag nanoparticles and CeO2-SBA-15 supports, and the strong MW absorption of CeO2 clusters that contribute to the MSIs during Ag deposition. The Ag particle sizes were controllably tuned from 1.9 to 3.9 nm by changing the loading amounts of CeO2 from 0.5 to 2.0 wt%. The Ag nanoparticle size was predominantly responsible for the high turnover frequency (TOF) of 0.41 min(-1) in ammonia borane dehydrogenation, whereas both particle size and MSIs contributed to the high TOF of 555 min(-1) in 4-nitrophenol reduction for Ag/0.5CeO2-SBA-15, which were twice as large as those of Ag/SBA-15 without CeO2 and Ag/CeO2-SBA-15 prepared by conventional oil-bath heating., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Silica supported amine materials are promising compositions that can be used to effectively remove CO(2) from large stationary sources, such as flue gas generated from coal-fired power plants (ca. 10 % CO(2)) and potentially from ambient air (ca. 400 ppm CO(2)). The CO(2) adsorption characteristics of prototypical poly(ethyleneimine)-silica composite adsorbents can be significantly enhanced by altering the acid/base properties of the silica support by heteroatom incorporation into the silica matrix. In this study, an array of poly(ethyleneimine)-impregnated mesoporous silica SBA-15 materials containing heteroatoms (Al, Ti, Zr, and Ce) in their silica matrices are prepared and examined in adsorption experiments under conditions simulating flue gas (10 % CO(2) in Ar) and ambient air (400 ppm CO(2) in Ar) to assess the effects of heteroatom incorporation on the CO(2) adsorption properties. The structure of the composite adsorbents, including local information concerning the state of the incorporated heteroatoms and the overall surface properties of the silicate supports, are investigated in detail to draw a relationship between the adsorbent structure and CO(2) adsorption/desorption performance. The CO(2) adsorption/desorption kinetics are assessed by thermogravimetric analysis and in situ FT-IR measurements. These combined results, coupled with data on adsorbent regenerability, demonstrate a stabilizing effect of the heteroatoms on the poly(ethyleneimine), enhancing adsorbent capacity, adsorption kinetics, regenerability, and stability of the supported aminopolymers over continued cycling. It is suggested that the CO(2) adsorption performance of silica-aminopolymer composites may be further enhanced in the future by more precisely tuning the acid/base properties of the support., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Blast furnace slag (BFS), a high-volume byproduct resulting from iron-making processes, can be considered as a low-cost and abundant precursor for preparing layered double hydroxide (LDH) compounds. Here we demonstrate that a Ca-based LDH compound (hydrocalumite) synthesized from waste BFS through facile two-step procedures and its derivatives work as useful heterogeneous base catalysts for multiple chemical reactions including the Knoevenagel condensation, oxidation of alkylaromatics with O(2), transesterification, and cycloaddition reaction of epoxides with atmospheric CO(2). Structures were verified by using XRD and thermogravimetric analysis. The surface basicity and coordination geometry of the active metal species that substantially affect the catalytic activity were investigated by CO(2)-temperature programmed desorption (TPD) and X-ray absorption fine structure (XAFS) measurements, respectively. These characterization results revealed that the slag-derived impurity elements, such as Fe, Ti, and Mn, effectively act either as active sites or as catalyst promoters in particular reactions and that the kind of guest counter anion (Cl(-) or NO(3)(-)) also plays a key role for achieving high catalytic efficiencies. In any reaction, the catalyst was easily separated by filtration and recyclable in multiple catalytic runs with retention of its activity and fine selectivity, irrespective of its considerable impurity level. It is believed that the slag-made hydrocalumite can replace existing LDH catalysts as a low-cost alternative and potentially contribute to sustainable chemical processes., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)