Design of Mesoporous Silica at Low Acid Concentrations in Triblock Copolymer-Butanol-Water Systems

Kleitz, Freddy,Kim, Tae-Wan,Ryoo, Ryong Korean Chemical Society 2005 Bulletin of the Korean Chemical Society Vol.26 No.11

Assembly of hybrid mesophases through the combination of amphiphilic block copolymers, acting as structuredirecting agents, and silicon sources using low acid catalyst concentration regimes is a versatile strategy to produce large quantities of high-quality ordered large-pore mesoporous silicas in a very reproducible manner. Controlling structural and textural properties is proven to be straightforward at low HCl concentrations with the adjustment of synthesis gel composition and the option of adding co-structure-directing molecules. In this account, we illustrate how various types of large-pore mesoporous silica can easily be prepared in high phase purity with tailored pore dimensions and tailored level of framework interconnectivity. Silica mesophases with two-dimensional hexagonal (p6mm) and three-dimensional cubi (Fm$\overline{3}$m, Im$\overline{3}$m and Ia$\overline{3}$d) symmetries are generated in aqueous solution by employing HCl concentrations in the range of 0.1−0.5 M and polyalkylene oxide-based triblock copolymers such as Pluronic P123 $(EO_{20}-PO_{70}-EO_{20})$ and Pluronic F127 $(EO_{106}-PO_{70}-EO_{106})$. Characterizations by powder X-ray diffraction, nitrogen physisorption, and transmission electron microscopy show that the mesoporous materials all possess high specific surface areas, high pore volumes and readily tunable pore diameters in narrow distribution of sizes ranging from 4 to 12 nm. Furthermore, we discuss our recent advances achieved in order to extend widely the phase domains in which single mesostructures are formed. Emphasis is put on the first synthetic product phase diagrams obtained in $SiO_2$-triblock copolymer-BuOH-$H_2O$ systems, with tuning amounts of butanol and silica source correspondingly. It is expected that the extended phase domains will allow designed synthesis of mesoporous silicas with targeted characteristics, offering vast prospects for future applications.

Design of Mesoporous Silica at Low Acid Concentrations in Triblock Copolymer-Butanol-Water Systems

Freddy Kleitz,유룡,Tae-Wan Kim 대한화학회 2005 Bulletin of the Korean Chemical Society Vol.26 No.11

Assembly of hybrid mesophases through the combination of amphiphilic block copolymers, acting as structure-directing agents, and silicon sources using low acid catalyst concentration regimes is a versatile strategy to produce large quantities of high-quality ordered large-pore mesoporous silicas in a very reproducible manner. Controlling structural and textural properties is proven to be straightforward at low HCl concentrations with the adjustment of synthesis gel composition and the option of adding co-structure-directing molecules. In this account, we illustrate how various types of large-pore mesoporous silica can easily be prepared in high phase purity with tailored pore dimensions and tailored level of framework interconnectivity. Silica mesophases with two-dimensional hexagonal (p6mm) and three-dimensional cubic (Fm m, Im m and Ia d) symmetries are generated in aqueous solution by employing HCl concentrations in the range of 0.10.5 M and polyalkylene oxide-based triblock copolymers such as Pluronic P123 (EO20-PO70-EO20) and Pluronic F127 (EO106-PO70-EO106). Characterizations by powder X-ray diffraction, nitrogen physisorption, and transmission electron microscopy show that the mesoporous materials all possess high specific surface areas, high pore volumes and readily tunable pore diameters in narrow distribution of sizes ranging from 4 to 12 nm. Furthermore, we discuss our recent advances achieved in order to extend widely the phase domains in which single mesostructures are formed. Emphasis is put on the first synthetic product phase diagrams obtained in SiO2-triblock copolymer-BuOH-H2O systems, with tuning amounts of butanol and silica source correspondingly. It is expected that the extended phase domains will allow designed synthesis of mesoporous silicas with targeted characteristics, offering vast prospects for future applications.

Catalytic conversion of syngas to higher alcohols over mesoporous perovskite catalysts

김태완,Freddy Kleitz,전종원,채호정,김철웅 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.51 No.-

Two types of mesoporous perovskite-type oxides (Meso-PTOs) were synthesized by combining atemplated synthesis and a citrate complex method. The Meso-PTO catalysts exhibited superior catalyticactivity in the higher alcohols synthesis from syngas compared to the bulk-PTO, likely due to theincreased dispersion of active sites on the high surface of the Meso-PTOs. Moreover, the Meso-PTOs showhigher productivity for C3 and C4 alcohols as well as C2+ oxygenates. Among the two Meso-PTOsdeveloped here, the mesoporous LaFe0.7Cu0.3O3 catalyst was capable of significant suppression of themethanation reaction and better selectivity to higher alcohols compared to the mesoporousLaCo0.7Cu0.3O3 catalyst.

Large pore phenylene-bridged mesoporous organosilica with bicontinuous cubic <i>Ia</i>3&cmb.macr;<i>d</i> (KIT-6) mesostructure

Guo, Wanping,Kleitz, Freddy,Cho, Kanghee,Ryoo, Ryong Royal Society of Chemistry 2010 Journal of materials chemistry Vol.20 No.38

<P>Assembly of mesostructured silica using Pluronic P123 triblock copolymer (EO<SUB>20</SUB>-PO<SUB>70</SUB>-EO<SUB>20</SUB>) and n-butanol is a facile synthesis route to the MCM-48-like ordered large mesoporous silicas with the cubic <I>Ia</I>3&cmb.macr;<I>d</I> mesostructure, which are designated KIT-6. This synthesis route has been successfully extended to phenylene-bridged organosilicas from the limit so far for silica, using 1,4-bis(triethoxysilyl)benzene as an organosilica source and re-optimizing the synthesis conditions. In particular, optimal acid concentration and reagent ratios were determined to allow facile synthesis of the bicontinuous cubic mesophase in high yield and high phase purity. The products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy, solid state NMR spectroscopy and analysis of nitrogen sorption at −196 °C using modern non-local density functional theory methods. This synthesis procedure enabled easy fine tuning of pore volume, specific surface area and mesopore size by variation of the hydrothermal aging temperature between 80 and 130 °C. Furthermore, wide angle XRD data suggest short range molecular-scale periodicity in the framework walls originating from regular arrangement of the bridging aromatic groups. These KIT-6 organosilica materials with fully interconnected nanoporous structure would be readily available for applications in heterogeneous catalysis, selective adsorption, and nanostructure design <I>via</I> solid templating approaches.</P> <P>Graphic Abstract</P><P>Phenylene-bridged mesoporous organosilica with a highly ordered <I>Ia</I>3&cmb.macr;<I>d</I> mesostructure was synthesized under acidic conditions by using triblock copolymer and butanol as mesopore-directing surfactant. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0jm01518k'> </P>

Catalytic conversion of syngas to higher alcohols over mesoporous perovskite catalysts

Kim, Tae-Wan,Kleitz, Freddy,Jun, Jong Won,Chae, Ho-Jeong,Kim, Chul-Ung THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2017 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.51 No.-

<P><B>Abstract</B></P> <P>Two types of mesoporous perovskite-type oxides (Meso-PTOs) were synthesized by combining a templated synthesis and a citrate complex method. The Meso-PTO catalysts exhibited superior catalytic activity in the higher alcohols synthesis from syngas compared to the bulk-PTO, likely due to the increased dispersion of active sites on the high surface of the Meso-PTOs. Moreover, the Meso-PTOs show higher productivity for C<SUB>3</SUB> and C<SUB>4</SUB> alcohols as well as C<SUB>2+</SUB> oxygenates. Among the two Meso-PTOs developed here, the mesoporous LaFe<SUB>0.7</SUB>Cu<SUB>0.3</SUB>O<SUB>3</SUB> catalyst was capable of significant suppression of the methanation reaction and better selectivity to higher alcohols compared to the mesoporous LaCo<SUB>0.7</SUB>Cu<SUB>0.3</SUB>O<SUB>3</SUB> catalyst.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Meso-PTOs were synthesized with different metal compositions and citric acid amounts. </LI> <LI> This paper firstly reported CoCu- and FeCu-based Meso-PTO catalysts for higher alcohol synthesis from syngas. </LI> <LI> Meso-PTOs showed high catalytic performance for the production of higher alcohols and C<SUB>2+</SUB> oxygenates compared with bulk-PTOs. </LI> <LI> Meso-FeCu-CA2 suppressed the methanation, and an enhanced the selectivities of C<SUB>3–4</SUB> alcohols and C<SUB>2+</SUB> oxygenates. </LI> <LI> Reaction temperature is one of the key parameters having the greatest effect on the CO conversion rate. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Tailor-Made Mesoporous Ti-SBA-15 Catalysts for Oxidative Desulfurization of Refractory Aromatic Sulfur Compounds in Transport Fuel

Kim, Tae-Wan,Kim, Min-Ji,Kleitz, Freddy,Nair, Mahesh Muraleedharan,Guillet-Nicolas, Ré,my,Jeong, Kwang-Eun,Chae, Ho-Jeong,Kim, Chul-Ung,Jeong, Soon-Yong Wiley Blackwell (John Wiley Sons) 2012 ChemCatChem Vol.4 No.5

Design of multicomponent photocatalysts for hydrogen production under visible light using water-soluble titanate nanodisks.

Dinh, Cao-Thang,Pham, Minh-Hao,Seo, Yongbeom,Kleitz, Freddy,Do, Trong-On RSC Pub 2014 Nanoscale Vol.6 No.9

<P>We report the design of efficient multicomponent photocatalysts (MPs) for H2 production under visible light by using water-soluble ultrathin titanate nanodisks (TNDs) stabilized by tetraethylammonium cations (TEA(+)) as building blocks. The photocatalysts are designed in such a way to significantly enhance simultaneously the efficiency of the three main steps in the photocatalytic process i.e., light absorption, charge separation and catalytic reaction. We show, as an example, the construction of water-soluble CdS-TND-Ni MPs. The designed CdS-TND-Ni MPs, in which CdS nanoparticles and TNDs are intimately assembled to enhance the charge transfer and surface area, are controlled in composition to optimize visible light absorption. The conception of the MPs allows them to be highly dispersed in water which markedly improves the photocatalytic H2 production process. Most importantly, a Ni co-catalyst is selectively located on the surface of TNDs, enabling vectorial electron transfer from CdS to TND and to Ni, which drastically improves the charge separation. Consequently, under visible light illumination (λ 420 nm), the optimally designed CdS-TND-Ni MPs could generate H2 from ethanol-water solution with rate as high as 15.326 mmol g(-1) h(-1) during a reaction course of 15 h and with an apparent quantum yield of 24% at 420 nm. Moreover, we also demonstrate that TNDs can be combined with other single or mixed metal sulfide to form water-soluble metal sulfide-TNDs composites which could also be of great interest for photocatalytic H2 production.</P>

Designed Synthesis of Mesoporous Solid-Supported Lewis Acid-Base Pairs and Their CO₂ Adsorption Behaviors

Zakharova, Maria V.,Masoumifard, Nima,Hu, Yimu,Han, Jongho,Kleitz, Freddy,Fontaine, Fré,dé,ric-Georges American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.15

<P>Conventional amines and phosphines, such as diethylenetriamine, diphenylpropylphosphine, triethylamine, and tetramethylpiperidine, were grafted or impregnated on the surface of metalated SBA-15 materials, such as <B>Ti</B>-, <B>Al</B>-, and <B>Zr</B>-SBA-15, to generate air-stable solid-supported Lewis acid-base pairs. The Lewis acidity of the metalated materials before and after the introduction of Lewis bases was verified by means of pyridine adsorption-Fourier transform infrared spectroscopy. Detailed characterization of the materials was achieved by solid-state <SUP>13</SUP>C and <SUP>31</SUP>P MAS NMR spectroscopy, low-temperature N<SUB>2</SUB> physisorption, X-ray photoelectron spectroscopy, and energy-dispersive X-ray mapping analyses. Study of their potential interactions with CO<SUB>2</SUB> was performed using CO<SUB>2</SUB> adsorption isotherm experiments, which provided new insights into their applicability as solid CO<SUB>2</SUB> adsorbents. A correlation between solid-supported Lewis acid-base pair strength and the resulting affinity to CO<SUB>2</SUB> is discussed based on the calculation of isosteric enthalpy of adsorption.</P> [FIG OMISSION]</BR>