I CG1:: O um* w w w universite montpellii I B ^^^^^^ SCIENCES ET TECHNIQUES Montpellier universite montpellier 2 depasser tes frontier es Non-Hydrolytic Sol-Gel Today • Principle of sol-gel process • Non-hydrolytic sol-gel process • Mixed oxides • Mesoporous mixed-oxide catalysts • Nanoparticles by NHSG Sol-Gel Process Low-temperature route to oxide materials Precursors Formation of :M-0-M= bridges jpolycondensation Sol Gel Vacuum/ \ Supercritical drying / \ Xerogel Aerogel Oxides Mixed-oxides Organic-inorganic hybrids • Porous solids: supports or catalysts "Hydrolytic" Sol-Gel Process Precursors H20 Polycondensation Xerogel { Densification Oxide glass Hydrolysis of alkoxides M-OR + H20 -► M-OH + ROH Condensation M-OH + M-OR -► M-O-M + ROH M-OH + M-OH -> M-O-M + H20 =^> Oxides, Hybrid Xerogels Porous oxide materials Monodisperse powders Coatings, Fibers, etc. Dense glass "Hydrolytic" Sol-Gel Process H20 Si02 Si(OEt)4 -> "Si02gel" -EtOH Silicon alkoxides: low reactivity (catalysis, H+, OH", F), easy =^> Simple routes to silica and hybrid materials Metal alkoxides: too reactive -> Precipitates (amorphous, hydrated oxo-hydroxides) -> Inhomogeneous mixed oxides ► Reactivity modifiers chelating ligands: carboxylic acids, p-diketonates... i=£> vlonhydrolytic Condensations completely different condensation reactions Conventional Sol-Gel process © Expensive alkoxide precursors © Disparity of hydrolysis-condensation rates: e.g. M(OR)n » Si(OR)4 -> Precipitates, heterogeneous mixed oxides © Low degree of condensation: Amorphous oxo-hydroxides, microporous materials => Complicated, expensive multi-step procedures... - prehydrolysis, modified precursors, multi-step acid-base procedures - templates, supercritical drying Why not try another reaction? Non-hydrolytic Sol-Gel process • Non-aqueous solvent, no water involved • Based on non-hydrolytic M-CI/M-OR condensation M-O-R + Cl-M T M-O-M + RCI R = Me, Et, 'Pr. M = Al, B, Fe, Ti, Zr, Nb, V, W, Mo... T = 80 - 150 °C M = Si: very slow => catalysis by Lewis acids : FeCI3, ZrCI4. Fundamentals of Non-Hydrolytic Sol-Gel • Non-aqueous solvent, no water involved • Based on non-hydrolytic condensations M-O-R + R'-C02-M -»► M-O-M + R'C02R M-OAc + R2N-M ->■ M-O-M + AcNR2 M-O-R+ R-O-M ->• M-O-M+ R20 M-O-R + X-M -*► M-O-M + RX M =AI, B, Fe.Ti, Zr, Nb, V, W, Mo... R = Me, Et, 'Pr... T = 80- 150°C M = Si: very slow => catalysis by Lewis acids : FeCI3, ZrCI4... Non-Hydrolytic Sol-Gel Routes • ln-situ formation of alkoxide groups: M-CI + R-O-R-► M-OR + RCI M-CI + R-OH -► M-OR + HCI (R = Et, Vr) -> M-OH + RCI (R = *Bu, Bz) • Alkoxide route MCIn + M(OR)n —I—> 2 MOn/2 + n RCI •Ether route MCIn + n/2 ROR—-—> MOn/2 + n RCI • Alcohol route MCIn +n/2 ROH —-—> MOn/2 + n/2 HCI + n/2 RCI Exchange and condensation reactions \ \ m-or + m-ci \ m. *0' r m—ci \ \ m-ci + m-or Nucleophilic attack of CI • at M : exchange (fast) xm_0-|\/ + rci • at R : condensation (slow) Precursors = mixture of chloroalkoxides RT TlCU + TltO'Pr^-> TiCI2(OlPr)2+ TlCyO'Pr) + TlCKO'PrJg 100 °c -iPrCI > 710, Condensation => cleavage of O-C bonds instead of O-H bonds Oxides by Non-Hydrolytic Sol-Gel • Crystalline metal oxide nanoparticles Colvin et al, J. Am. Chem. Soc. 1999, 121, 1613. Niederberger et al J. Am. Chem. Soc 2002, 124, 1 Hyeon et al, J. Am. Chem. Soc, 2003, 125, 6553. Mutin et al, Chem. Mater. 2010, 22, 4519. • Metal oxide thin films: Ritala et al, Science, 2000, 288, 319. Mutin et al, Chem. Mater. 2009, 21, 2577. • Mesoporous mixed oxides: Devillers et al, Catal. Today 2003, 81, 77 Mutin et al, Chem. Mater. 2009, 21, 2817 Ricci et al, Appl. Catal. A 2010, 389, 147 Mutin et al, Chem. Commun. 2011,10728 • Metal oxide foams: Grader et al. Ceram. Trans., 1998, 95,161. US Patent 2004, Cellaris Ltd., Israel Mixed Oxides by Non-Hydrolytic Sol-Gel 1-step reactions, no reactivity modifier: T Alkoxide route: MCL + z M'CL +1 M'(OR)n. -* MxOn/2 .M'(z+t)On,z+ -RCI Ether route: MCIn + z M'Cln. + (n+n'z)/2 ROR ^ > MOn/2.z M'On/2 Exchanges => mixture of chloroalkoxides MCIx(OR)n.x + M'Clx.(OR)n..x. => M—O—M' + M—O—M + M'—O—M' Si02-MOx systems: condensations around Si catalyzed by M species: -> levelling of reactivities around Si and M -> Highly homogeneous xerogels Nonhydrolytic Si02 - Zr02 Si(OjPr)4 + ZrCI4 110°c, 500°C,5h^ CH2CI2 Air 29Si MAS NMR -100 8/ppm Si-O-Zr bonds, homogeneous -140 Si Si o o Si-O-Si-O-Si Si-O-Si-O-H 6 8-109 6 8-100 Si Si Si M O O Si-O-Si-OM Si-O-Si-OM 6 8-102 0 8-96 Si M 6 i Si M 6 i Si-O-Si-OM M-O-Si-O-M 6 8-90 68-86 M M J. Mater. Chem. 1996 6, 10 Structure of nonhydrolytic Ti02-Si02 10 SiCI4 + 9 Si(0'Pr)4 + ■n(0'Pr)4 110°C> XRD 1540 °C, 1 h -a_A_ 1300 °C, 2h JL 900 °C, 2h liifih. 600 °C, 5h J_i_I_i_I_i_L 5 10 15 20 25 30 35 40 26/degrees calcination Solid solution Single phase cristobalite Random subst. of Si by Ti Tetragonal unit a = 5.00 A (Si02: 4.97 A) c = 6.98 A (Si02: 6.93 A) J. Mater. Chem. 1996 6, 10 Al203 - Ti02 system 2 AICI3 + TiCI4 + 5 jPr20 110°9 T°C, 5h CH2CI2 Air T(°C) Liquid__ 1800 ■ 1500 Ti02 + AI2Ti05 Al203 + AI2Ti05 1200 ■ Ti02 + Al203 Ti02 25 50 75 Al203 Mol% SGNH: Direct crystn of P-AI2Ti05at 600 °C! Powder XRD Chem. Mater. 1997 9, 1098 1200°C 10 15 20 25 30 35 Theta /degrees 40 Si02-Ti02 mild oxidation catalysts Hydrolytic sol-gel: simultaneous control of Ti dispersion and texture difficult -> complicated, multi-step procedures > Ti dispersion: reaction rates around Ti » Si -> 77 precursor modification, pre-hydrolysis, acidic conditions > Texture: evaporative drying -» high capillary pressure Pc acidic conditions -> low degree of condensation -> pore collapse -> microporous xerogels Brinker, C. J.; Scherer, G. W. Sol-gelSciencel990. Hutter, R.; Mallat, T.; Baiker, A. J. Catal. 1995, 157, 665. Klein, S.; Thorimbert, S.; Maier, W. F. J. Catal. 1996, 163, 476. Si02-Ti02 mild oxidation catalysts > Avoiding pore collapse =^> templates, supercritical drying: expensive... =^> solvent exchange with hexane + silylation: Pc = -2ycos9/r y : surface tension; 6: contact angle; r: pore radius Yhexane 18-4 mN/m < Ywater 72-8 mN/m -> decreases PC silylation: OH surface groups replaced by OSiMe3 no H-bonding, no condensation reversible shrinkage Prakash et al. Nature 1995, 439 Sotelo et al. Chem. Comm. 1999, 549 "Non-hydrolytic" Si02-Ti02 Etherolysis: =M-CI + jPr-0JPr -► =M-OjPr + jPrCI Condensation: em-O-iPr + =M-CI -> =M-0-M= + 'PrCI M = Ti: easily controllable kinetics, condensation at 80-150 °C M = Si: very slow but condensations catalyzed by Ti species homogeneous mixed oxide xerogels even for Si02-MOx systems no need for multi-step procedures or complicated precursors Irreversible condensation -> very high condensation degrees up to 90% Chem. Mater. 2004, 16, 5380 f,Non-hydrolyticM Si02-Ti02 Liquid phase: PrCI + CH2CI2 yiPrCI: 24 mN/m yCH2CI2 : 26.5 mN/m < yH20 : 72.8 mN/m -> low capillary pressure Surface groups: no OH, only CI and OiPr no H-bonds, no condensation at ambient T: -» reversible shrinkage No need for solvent exchange and silylation -> mesoporous xerogels if the degree of condensation is high enough NH SiOo-TiOoi control of texture CH2CI21.2 vol 5.5 SiCI4 + 4.5 Si(OPr)4 + Ti(C}Pr)4 N° S0'vent , ^"9 , No liquid phase 4d Vac.150°C V H. (cm3/g) ads 800- 600- 400- 200- 0 ZCT A' / A / A' a a' „j ^-□□LXDnQEELX ■ £»O-OK3KX^C0O-(D-(CKD-cd-0 od^^ TS-1 - |gg.o_o—ooooooooooooo-o—o—o—o—o—o-oo-oooco-a^ >.o- 0 0.2 0.4 0.6 0.8 Relative Pressure 1.0 DRUV-vis NH Si02-Ti02 250 300 350 400 450 Wavelength / nm 3.3 wt%Ti, outstanding texture, good Ti dispersion Chem. Commun., 2008, 5357 Si02-Ti02 oxidation catalysts Oxidation of bulky compounds by aq. H202 (0.1 M) _ 2 H202 60 °C, 2 h [NH Si02-Ti02] _ cAo DBTS>99 % 97% conv. in 2 h 98% H202 efficiency TOF:21 h1 (TS1:3h1) 5 H202 60 °C, 6 h [NH Si02-Ti02] AQ>95% 92% conv. in 6 h 91% H202 efficiency • accomodates very bulky substrates • good activity, excellent H202 efficiency, reusable (»Ti-MCM41) Chem. Comm. 2008, 5357; Appl. Catal., £2010, 97, 407 Hybrid Si02-Ti02 epoxidation catalysts 110°C TiCI4 + 6 MeSiCI3 + 4 SiCI4 + 19 'Pr20 SiTi-T 1060m2/g 1.3cm3/g TiCI4 + 2 Me3SiCI + 8 SiCI4 + 19 iProO 110°C 2^-- SiTi-M 930 m2/g 0.7 cm3/g 29Si MAS-NMR T SiTi-T JI Q M i A Q II SiTi-M 0 -50 -100 8 (ppm) 0 Epoxidation test 20 40 60 Reaction time / min 80 Excellent activity, selectivity >99 % WO2005049626; Chem. Mater. 2006,18, 4707 Ti02-V205 catalysts • Selective Catalytic Reduction of NOx by NH3 • Selective oxidation of H2S •Total oxidation of Volatile Organic Compounds • Oxidative dehydrogenation of propane Conventional catalysts: impregnation of Ti02-anatase supports -» monolayer of vanadate species Ti02-V205 catalysts Nonhydrolytic synthesis: ether route, chloride and oxychloride precursors Relative Pressure (P/PO) Pore diameter / nm Mesoporous, ca 80 m2/g, narrow pore size distribution Ti02-V205 catalysts SEM Aggregates of spherical particles (2-7 Mm) built of uniform nanoparticles (10-20 nm) Hierarchichal texture, self-assembly of nanoparticles Ti02-V205 catalysts XRD Raman 30 40 29 / deg. ToF-SIMS 60 Impregn. -i-1-1-r"""1!1"—i-1-1-iiiWplM"i-1-1-r- 400 600 800 1000 Wavenumber / cm"1 Polymeric and monomeric V species dispersed on anatase Surface species similar to catalysts prepared by impregnation Ti02-V205 catalysts • Selective Catalytic Reduction of NOx by NH3: Collaboration G. Delahay, B. Coq, ICG Montpellier 4NO + 4NH3 + 02 250 - 350°c> 4N2 + 6H20 Catalyst Chem. Commun. 2004, 2214; Appl. Catal. B2006, 69, 49. • Total oxidation of Volatile Organic Compounds : Collaboration Damien Debecker, Eric Gaigneaux, UCL f~\ —^-^ C02 + H20 \=/ Catalyst Appl. Catal. B2010, 94, 38; Catal. Today 2010 Activity comparable to the best conventional catalysts Ti02-V205 catalysts Selective Catalytic Reduction of NOx by NH3: Collaboration G. Delahay, B. Coq, ICG Montpellier 250 - 350°C ^ 4No + 6Ho0 4 NO + 4 NH3 + 02 Catalyst Chem. Commun. 2004, 2214; Appl. Catal. B2006, 69, 49. % NO conversion 100 80 60 40 20 0 ppm N20 1000 NHV-Ti / o o Eurocat o p p ■ o 800 600 400 200 0 400 450 500 550 600 Temperature / K Comparison of: NH V205-Ti02 vs. Eurocat catalyst Conditions: Continuous flow, 20 mg cata., Gas flow: 138 cm3/min Feed: 0.2 % NO, 0.2 % NH3, 3 % 02 in He Highly active: • at 500 K: 50 % conversion 8 ppm N20 • No loss of activity after 100 h at 573 K. • No S02 poisoning (25 ppm) Ti02-V205 catalysts Collaboration D. Debecker, E. Gaigneaux, UCL Comparison: impregnated vs. nonhydrolytic catalysts: ToF-SIMS: Similar surface species XPS : surface composition - xerogel: V/Ti =0.05 - calcined xerogel: V/Ti =0.13 - impregnated catalyst: V/Ti =0.17 => Migration of VOx species toward the surface during calcination Impregn. TiV05-. A.............i v2o5-Ik. i i A»i i NHSG - ,kL. JIL . LJkiL_ .hj. „1 L i 500 °C 5 h Appl. Catal. £2010, 94, 38. Si02-AI203-Mo03 metathesis catalysts Collaboration: D. Debecker, E. Gaigneaux (Louvain la Neuve) M. Stoyanova, U. Ftodemerck (Rostock) Olefin metathesis: propene synthesis CH CH + CH-CH3 Mc^/AIA CH2 ^ w 2 CH-CH3 CH-CH3 Conventional catalysts: •Molybdate species grafted to an alumina or acidic silica-alumina support •Most active species: isolated molybdates Phillips Petroleum Co o o / o \ Mo V° I Si02-Al203 Si02-AI203-Mo03 metathesis catalysts x SiCI4 + AICI3 + y MoCI5 Si/AI = 15; 5-20 wt% MoO-_TEM 110 °C, 4d CH2CI2 Drying ^ Calcination > 110 °C, Vac. Air, 500°C, 5h 100 nm NH10%MoO, 1000KO) 4 co 3 co 750 E o 5 500 h O if) 250 - 0 Li 2 o o 1 0 / it □ □ / 20 100 Pore Diameter / □ SBET=480 m2/^ Vp=1.6,cm?/g Cfrem. Mater. 2009, 21, 2819 0.0 0.2 0.4 0.6 0.8 Relative Pressure 1.0 Si02-AI203-Mo03 catalysts nh3-tpd NH Si/AI/Mo 10% MoO. 100 200 300 400 500 Temperature / °C XPS surface analysis o 4- _+ < + 53 + 2- 0 - NH-calc ■ ________ ■ Wl ' u NH-fresh 1 1 1 1.1.1. 1.1. 6 8 10 12 14 16 18 20 M0O3 loading / wt% Si/AI/Mo: Acidic sites, mixed Si02-Al203 "support" Calcination: Migration of MOx species toward the surface Si02-AI203-Mo03 catalysts TOF-SIMS: Surface species, comparison between NHSG and Wet Impregnation NH catalyst: Chem. Mater. 2009, 21, 2819 TOF-SIMS MoO 146 3 144 140 14? 12412713932 ^ .....\.....iA-M-H............ Wl 8% MoO, 148 15^5«??? 165 12Š30 101 105108 111 1^16 1?0 1fl26jll32 only monomeric MoOx 100 species at the surface. 110 1^16 120 H26I I 132 I 120 130 146 140 4jJ 143 uu NH 10% MoO 148 16062 "T"—t"-lT""^""T'"'Tl 140 150 160 170 MOoO „ ^ WI8%MoO Mo309- 433.c-, 491 636 47=1 47480JL 51252838552566579392 62ÍM. 676 300 400 500 600 Si02-AI203-Mo03 catalysts Self-metathesis of propene: 2 40 °C [NH Si-AI-Mo] + t-1-1-1-1-1-r I 1 I 1 I 1 I U 5 wt% 10 wt% 15 wt% 20 wt% Mo03 M0O3 M0O3 M0O3 Catal. Sci. Technoi 2012, 2, 1157-1164 Si02-AI203-Mo03 metathesis catalysts Self-metathesis of propene (LIKAT: M. Stoyanova, U. Rodemerck) 40 °C [NH Si-AI-Mo] + 40- ^= CO 30- o E ■ E 20- > o 10- < 0-0 Comparison with catalysts prepared by * methods: NHSG: up to twice higher specific activity 5 10 15 MoO_ loading / wt% Non-hydrolytic routes to nanoparticles Extremely successful in the synthesis of metal oxide nanocrystals N. Pinna, M. Niederberger, Angew. Chem., 2008, 47, 5292. • Surfactant-assisted syntheses: e.g. TiCI4 + Ti(0'Pr)4 300 °C TiO TOPO V. L. Colvin et al, J. Am. Chem. Soc. 1999, 121,1613 Benzyl alcohol route: 100 °c e.g. WCI6 WO- PhCH2OH M. Niederberger et al J. Am. Chem. Soc 2002, 124,13642 • Silica-based amorphous nanoparticles? • Ether route? in the absence of surfactant? Si02-Ti02 nanoparticles Stober synthesis: does not lead to homogeneous Si02-Ti02 nanoparticles (precipitation of Ti02) 9 SiCL + T1CL + 20 Vro0 CHoCI. V solv /Vprec=15 Sealed tube 110°C,5d Reaction stopped before gelation by cooling down to RT TEM UV-Vis 300 400 500 Wavelength / nm • Homogeneous Si02-Ti02 unaggregated nanoparticles Chem. Mater. 2009, 21, 2577. Si02-Ti02 nanoparticles: influence of Si/Ti ratio x SiCL + TiCL + 2x+2 iProO CHoCI 2^'2 Evap. *■-!-> 110 °C, 5d TEM 10 mol% Ti 15mol%Ti 30 mol% Ti , KB * s am m mmm *>* a UV-Vis 10mol%Ti 30 mol% Ti From homogeneous to core-shell Si02-Ti02 nanoparticles 300 400 500 Wavenumber / nm Stability of Si02-Ti02 sols - stable at RT (in the absence of water) - can be concentrated and redispersed in organic solvents in the absence of surfactants or electrostatic repulsions! Stabilization mechanism of Si02-Ti02 sols 29Si CP-MAS NMR FTIR 5 / ppm Wavenumber / cm CI and OiPr surface groups, no OH groups Organophilic nanoparticles: solvatation No nonhydrolytic condensation at RT « Kinetic stabilization » of the sol Chem. Mater. 2009, 21, 2577. Application: polymer nanocomposites Solution of NP and PMMA in CH2CI2 Casting Transparent PMMA-Si02 nanocomposite TEM image of a microtome cut: (70 nm thick) Perfect dispersion, no need to modify the NP surface Application: nanoparticle monolayers No surfactant, Si-CI and Si-OiPr surface groups =^> reactive surface oh oh oh oh oh oh 9h oh immersion )pQ y S< ^ in a sol ^—1—1—1—1—'—'—*- -HX 1 1 Si Wafer Grafted NPs Topography / nm Monolayer of NP, whatever the immersion time => self-limiting grafting of NP Ti02 nanoparticles TiCL + 2 'Pr,0 CHoCI 2v-"2 T °C, 60 h TEM X Am 150 °C 110 °C 80 °C T/°C Sbet (mV) Dbet fnm) (nm) 80 430 3.6 3.8 110 170 9.1 9.5 150 105 14.7 16.3 20 30 40 50 60 70 80 2 9/ degree Chem. Mater. 2010, 22, 4519-4521 Ti02 nanoparticles wafer immersed in a sol of TiO280 nanoparticles in THF (0.3 wt% Ti02) for 2 hours at 25 °C Silica and Siloxane Organic-Inorganic Hybrids by NHSG Hydrolytic Sol-Gel: mild conditions introduction of organic groups via Si-C bonds 0 O O R 1 I I I O—Si— O R—Si—O R—Si—R R—Si—O O O O R Q T D M Applications: protective coatings, optics, electronics, catalysis, chromatography, membranes... Silica xerogels by Non-Hydrolytic Sol-Gel a 600 siCI. + Si(OiPr)., 0.1% FeCI | 500-2 400-I 8 300 H "D (0 CD 200-100- o > 0 0.0 300 £ 200 o mesoporeux 0.2 0.4 0.6 0.8 Pression Relative SiCL + Si(OChLPh) 1.0 microporeux + mesoporeux o 0.0 0.2 0.4 0.6 0.8 Pression Relative 1.0 700-1 ■ co 600- E 500- ■ .Q s_ 400- o ■ o-l SiCL+PrJD, 0-1% FeCI non poreux 0.0 0.2 0.4 0.6 0.8 Pression Relative Wide range of textures depending on the conditions •O-donor • time, temperature, catalyst •liquid phase volume 1.0 Catalysis of condensations around Si Lewis acid FeCI3 > ZrCI4 > AICI3 > TiCI, —Si-OR + >e-c'/ \- >e-CI -Si-O-R ' Sc Fe-CI v-RCI FeCI3: 0.1 mol% is sufficient to form Si02 =^>1 FeCI3 catalyzes the formation of 2000 Si-OSi bonds! Competition between catalysis and incorporation in the Si02 network Silica and siloxane hybrids by NHSG Non-Hydrolytic Sol-Gel: = 100°C, Lewis acids, alkyl chlorides mild conditions ? Friedel-Crafts reactions? Exchange or cleavage of Si-C bonds? Si-H bonds? ■ > Synthesis of model silsesquioxanes (T resins) R-Si015 R = Me, C18H35, Vi, Ph Silsesquioxanes by NHSG: Reaction Conditions 1 % Lewis acid MeSiCI3 + MeSiOEt3-- 2 MeSiC^ 5 + 3 Et-CI Lewis acid FeCI3 > ZrCI4 > AlClg > TiCI4 Gel times 0.5 h 10 h 60h 140 h MeSiCI3 + R'20 0.1%FeCI3_^ MeSio15 + 3R'-CI 110 °C Oxygen donor MeSi(OEt)3 >Pr20 Et20 Gel times Condensation 5h 10 h 60 h >95% >95% 90% Silsesquioxanes by NHSG „ ^ 0.1% FeCU R-SiCU + 'Pro0 — 3 110 °C R = Alkyl, Vinyl • high degree of condensation • No Si-C redistribution • No Si-C cleavage R = Phenyl • Sealed tube: cleavage of Si-Ph bonds by iPrCI • Open system: no cleavage J. Sol-Gel Sci. Tech. 14, 137 (1999) J. Mater. Chem, 10, 1811 (2000) R-SiCvg + 3 ^rCI 29Si CP-MAS NMR MeSi015 -20 -60 -100 8 (ppm) Methoxylated D/Q resins by NHSG i i 0 o 1 i Goals: Me—Si—Me —O—Si—o- -1 step synthesis ^ 9 - resins built of: D units Q units - terminated by Si-OMe functions (curing by hydrolysis) Application: adhesives for silica fibers Hydrolytic syntheses: no control on the viscosity => NH synthesis Cata 0.4 Me2SiCI2 + 0.6 Si(OMe)4 -* (SiMe2)0 4(Si)0 6O0 8{OMe)^ 6 + 0.8 MeCI A No solvent, 1-step, MeCI: recycled in the synthesis of methylchlorosilanes EP 728793 Al 1996; J. Polym. Sci. Part A 1998, 36, 2415. D/QOMe Resins: Choice of Reaction Conditions First try: - FeCI3 catalyst: I > Solid! Hydrolysis? Distillation? => Reaction in sealed NMR tubes, monitoring by 1H NMR Formation of Me20 2 Si-OMe -* Si-O-Si + Me20 t degree of condensation (Si-O-Si) Other catalysts??? 5 4 3 2 1 0 -1 8 (ppm) Looking for a Selective Catalyst Test reaction: 0.4 Me2SiCI2 + 0.6 Si(OMe)4 130 °C, 1%cata - 16h. sealed NMRtube Selectivity % MeCI 100-, H VCI 90 H ■ 80- 70- 60- 3 CeCI. o TiCI NbCI, ZrCI4 Cp2ZrHCI ■BiCL FeCL (0.1%) AICI. Yb(OTf). La(OTf). 20 40 60 80 100 Reaction extent Reactivity Influence of Reaction Temperature Reaction: 0.4 Me2SiCI2 + 0.6 Si(OMe)4 T, 1 % cata sealed NMR tube %MeCI Selectivity 100- 95- 90- 85- 80 140°C 125°C 105°c ZrCI, 200*C 200°C TiCI, 0 25 50 75 100 125 Length of reaction (hours) Synthesis of D/Q0Me Resins Conditions: • Me2SiCI2 and Si(OMe)4 • 1 % ZrCI4 • 130 to 150°C, autoclave or sealed tube <=> Orange liquids, well-controlled viscosity Samples Viscosity (cP) 0.3 Me2SiCI2 + 0.7 Si(OMe)4 -* D/Q 30/70 2-5 0.4 Me2SiCI2 + 0.6 Si(OMe)4 -- D/Q 40/60 7.3 0.5 Me2SiCI2 + 0.5 Si(OMe)4 -* D/Q 50/50 53 Characterization: GC/MS. 29Si NMR Structural units in D/Q0Me Resins OMe I Me-Si-Me OMe OMe I Me-Si—Me I 0 1 I 0 1 Me-Si-Me 0 1 D° D2 OMe I MeO—Si—OMe I OMe I OMe O OMe I I I MeO—Si—OMe MeO—Si—OMe —O—Si—O I 0 1 — —o- I 0 1 Si—O I 0 1 Q° Q Q2 Q3 Qt GC/MS (D/Q 40/60) 1 % ZrCI 0.4 Me2SiCI2 + 0.6 Si(OMe)4 —--^— 130 °C d0 + q° + d1-d1 d1-q1 D1D2D d1q2d1 d1d2q1 q1-q1 Q1Q2Q1 q1d2q1 \ d1-q3-d1 I 1 d d1 d2d2q1 d1 d2q2d1 + ■ ■ ■ r D1_Q3_D1 I 1 q d1d2q2q1 d1q2d2q1 +... q2 y d2-q2 Q1_q3_d2 d2-q2 +... 4 0 0 6 0 0 8 0 0 10 0 0 Scan Quantitative 29Si NMR (D/Q 40/60) Me Me-Si-OMe l OMe D° 0 Me I Me-Si-OMe I O- D2 Me I Me-Si-0- I O- La OMe I MeO-Si-OMe OMe MeO-Si-OMe Q0 I OMe I O- Q OMe MeO-Si-0- l O- Q2 OMe -O-Si-O- I O- Q3 o- -O-Si-O- i o- t-r -100 -20 -40 -60 -80 ppm Good control of the composition: D/Q = 39/61 O/Si = 0.85 (th. 0.80) => Controlled viscosity of the resins 29Si NMR (D/Q 40/60) D° D1Q J T 0 "T ■10 Q1 Q ^ D-Q2D 1 Q-Q2D T -20 ~~r -80 Q-Q2Q ■90 —r -100 ~I— ppm Good homogeneity: High level of D-Q bonding Statistics: random distribution of Si-OMe and Si-OSi bonds High T, Lewis acid: Condensation and Redistribution of Si-OX bonds Excellent reproducibility and stability of the resins Conclusions: Non-Hydrolytic Sol-Gel: Changing reactions, changing reaction medium: - Impacts reaction kinetics, condensation degree - facilitates control of composition, homogeneity, texture -Avoids using alkoxide precursors, reactivity modifiers, multi-step procedures, templating, supercritical drying... Importance of thermal treatment of the xerogel - Removal of residual OR and CI groups - Migration of the less refractory oxide species => Attractive one-step routes to efficient mixed oxide catalysts Collaborations Ďamien Debecker, Eric (Saigneaux (Louvain-la-Neuve, Belgium) Vasile Hulea (MACS-IC6M) Emil Ďumitriu (Iasi, Romania) Gerard Delahay, Bernard Coq (MACS-IC6M) Uwe Rodemerck, Mariana Stoyanova (LIKAT, Rostock, Germany) CHEMISTRY OF MATERIALS FIMVAIT 3«, 39B* VOIVM II 4 ^.•<>,*>,A" Recent reviews: Chem. Mater. 2009, 21, 582-596. Chem. Soc. Rev. 2012, 2624-2654. Perspectives: Hierarchical oxides using cellulosic materials Cellulose: 50 wt% O, in alcohol and ether groups. O-donor? template? Cotton Wool Cellulose Ferula Pith Titania from cotton wool CTi02 calcined at 400 °C Nice hierarchical fibrillar structure Titania from ferula pith Hierarchical cellular structure