MESOCHEMISTRY SYNTHESIS IN “INTERMEDIATE” DIMENSIONS

Geoffrey A. OzinMaterials Chemistry Research Group

University of Toronto

CHEM 1270H: TOPICS IN INORGANIC CHEMISTRY

Tel: 416 978 2082, Fax: 416 971 2011E-mail: gozin@chem.utoronto.ca

Group web-page: www.chem.toronto.edu/staff/GAO/group.html

MESOCHEMISTRYSYNTHESIS IN “INTERMEDIATE” DIMENSIONS

• Purpose of the four lectures • Introduce key physicochemical design principles that

underpin the template directed synthesis of inorganic mesoporous materials

• Focus on synthetic control of structure, composition and form

• Appreciate how the properties of materials fashioned at this intermediate length scale can be orchestrated to create a purposeful function directed to a specific field of use.

Angew Chem 2006, 45, 3216

ZEOLITESCRYSTALLINE MICROPOROUS ALUMINOSILICATES

WITH PORES AND CHANNELS IN SIZE RANGE 0.3-1NM

ISI Citations

6386

ESCAPE FROM THE 1NM ZEOLITE PRISONESCAPE FROM THE 1NM ZEOLITE PRISON

ESCAPE FROM 10 Å PRISON

• Discovery by Mobil researchers that an assembly of surfactant molecules could function as a supramolecular template for organizing and polymerizing silicates

• Produced the first fully characterized examples of periodic hexagonal and cubic forms of mesoporous silica with pore diameters 2-10 nm

• Integration of surfactant and sol-gel chemistry

Air drying

SC CO2 drying

SOL-GEL CHEMISTRY

SOL-GEL CHEMISTRY

Air drying

SOL-GEL CHEMISTRY

Base catalyzed hydrolytic poly-condensation of silicon alkoxides to silica

SOL-GEL CHEMISTRY

Acid catalyzed hydrolytic poly-condensation of silicon alkoxides to silica

• HYDROLYSIS

• (RO)3SiOR + H3O+ (RO)3SiORH+ + H2O

• 2H2O + (RO)3SiORH+ (RO)3SiOH + ROH + H3O+

• CONDENSATION

• (HO)3SiOH + H3O+ (HO)3SiOH2+ + H2O

• (HO)3SiOH + (HO)3SiOH2+ (HO)3SiOSi(OH)3 + H3O+

SOL-GEL CHEMISTRY

Lyotropics

Kraft T

CO-ASSEMBLY

SURFACTANT AND SOL-GEL CHEMISTRY

MILESTONES IN MESOPOROUS MATERIALS

• Escape from the 1 nm prison (surfactant templated synthesis)• Diagnostics (structure, property)• Structure control (H, C, L, WH)• Template removal (calcination, ion exchange, solvent extraction,

photocalcination, ozonolysis, microwave, lizard fragmentation)• Pore size control (surfactant, block copolymer, swelling additive)• Templating mechanism (micelle, liquid crystal)• Smart mesostructure (pore size expansion, metamorphic channels)• Free-standing and supported film (mesoepitaxy, pore orientation)• Topological defects (nucleation, growth, origin of curved pores and form)• Morphogenesis of curved shapes (fiber, discoid, gyroid, spiral, sphere)

MILESTONES IN MESOPOROUS MATERIALS

• Nanomeso (nanoscale particles, nanocrystalline texture)• Biomimetics (biomineralization connection, hierarchy (nm-micron length

scales), complexity, organic-inorganic nanocomposites or hybrids)• Panoscopic materials (global self-assembly over “all” scales, surfactants,

block copolymers, opals)• Patterning (microcontact printing, micromolding in capillaries,

microtransfer printing, ink jet printing, photolithography)• Smart guests (SC, M, OM, C, P)• Smart channels (terminal and bridging organofunctionality)• Beyond silica (metals, oxides, sulfides, phosphates, coordination, polymers)• Mesoreplication (carbons, metal oxides)• Function and utility (fuel cell, solar cell, battery, laser, low-k, controlled

chemical and drug release, chemical/biosensor, electrochromic display, 1D Bragg photonic crystals, low refractive index optical cladding )

pH, pH, pH

EFFECT ON SELF-ASSEMBLY MECHANISM

Temperature

Ageing conditions

Precursor

Surfactant

pHCatalyst

Concentration

Template removal

HYDROLYSIS, CONDENSATION, SELF-ASSEMBLY

ESCAPE FROM 10 Å PRISON

HEXAGONAL MESOPOROUS SILICA

100

110

200

210

hexagonal

cubic

lamellar

Nitrogen gas adsorption isothermsSmall angle X-ray diffraction

Microporous < 2 nm

Mesoporous 2 -50 nm

Macroporous > 50 nm

IUPAC CONVENTION FOR PORE SIZES

CUBIC BICONTINUOUS MESOPOROUS SILICA

Equipotential minimal energy surface

Cubooctahedral morphology

TEM image cubic mesoporous structure

Mesocrystalline glass – crystalline mesoporosity - periodic arrangement of mesopores – glassy

walls - long range order at mesoscale – short

range order at microscale

WHAT CAN WE DO WITH PMS MATERIALS?HOST-GUEST INCLUSION WITH LARGE GUESTS !!!

ORGANICALLY FUNCTIONALIZED PMS - GRAFTING

CLEVER USE OF GRAFTING CONTROLLED RELEASE OF ACTIVE COMPOUNDS

NANO-PMS SMART DRUG

DELIVERY AFM 2007

ORGANICALLY FUNCTIONALIZED PMS - COCONDENSATION

PHOTOCHEMICAL SWITCHPORE SIZE CONTROL

Synthesis of films bearing photosensitive azobenzene units: 4-(3-triethoxysilyl-propylureido) azobenzene by the coupling of triethoxysilylpropylisocyanate with 4-phenylazoaniline used as organosilane precursor in co-condensation reaction

Periodic mesoporous silica with channel walls functionalized with terminally bound alkanethiol groups that chelate and sequester toxic heavy metals.

HEAVY METAL SPONGE

PERIODIC MESOPOROUSN ORGANOSILICAS PMOs

ZOO OF PMO PRECURSORS

Acc. Chem. Res. 2005, 38, 305-312.

MATERIALS CHEMISTRY SOLUTION TO THE LOW k CHALLENGE

Periodic mesoporous organosilicates PMOs with organic cross-links!!!

Hatton, B.D., Landskron, K., Hunks, W.J., Bennett, M.R., Shukaris, D., Perovic, D.D., Ozin, G.A., New Materials Chemistry Approaches for Low Dielectric Constant Materials as Interlayer Dielectrics, Materials Today 2006, 9, 22.

METAMORPHIC CHANNEL WALLS – PMO BRIDGE TERMINAL EXCHANGE

PMO WITH ORDERED BRIDGING AROMATIC GROUPS IN THE CHANNEL WALLS

MOLECULAR MODEL OF THE ORDERING OF BRIDGING BENZENE GROUPS IN THE CHANNEL WALL OF BENZENE PMO

MOLECULAR MODEL OF THE ORDERING OF BRIDGING THIOPHENE GROUPS IN THE CHANNEL WALL OF THIOPHENE PMO

BIFUNCTIONAL PMOs

The Idea – PMO to MIPMOThe Idea – PMO to MIPMO

IMPRINTIMPRINT IMPRINTIMPRINT

the ideathe ideaIMPRINTIMPRINT

imprintimprintremovalremoval

imprintimprintmoleculemolecule

collaborationcollaborationJean-Christophe Leroux (CRC in Drug Delivery)Jean-Christophe Leroux (CRC in Drug Delivery)

Nature NanotechnologyNature Nanotechnology. . 20072007, , 22, 679-684., 679-684.

MIPMOs

Schematic of the synthesis of molecular imprinted periodic mesoporous organosilica MIPMO materials

Drug-PMOsDrug-PMOscommercially available drugs commercially available drugs

↳↳silsesquioxane PMO precursorssilsesquioxane PMO precursors↳↳assemble MIPMO structuresassemble MIPMO structures

↳↳remove the drug imprintsremove the drug imprints↳↳detoxificationdetoxification

calcium channel blockerscalcium channel blockers

VerapamilVerapamilDiltiazemDiltiazem

Drug SilsesquioxanesDrug Silsesquioxanes

MESOPOROUS MATERIALSGRAND CHALLENGES – UTILITYUTILITY

• Large (bio)molecule catalysis• Polymerization nanoreactor• Membrane separation• Chromatography stationary phase• Fuel cell anode• Lithium battery electrolytes• Electrochromic display• Solar cell photo-cathode• (Bio)chemical sensor• Drug storage and release vehicle• Heavy metal sponge• Low dielectric constant film• Low refractive index optical cladding• Lithographic masks• Nanofluidic ion channels• Nanocomposites