A New Methodology to Functionalize Surfaces of Ordered Mesoporous Materials Based on Ion Exchange Reactions

Abstract

It is now well known that mesoporous inorganic materials with extremely high surface areas and ordered mesostructure can be synthesized through sol-gel reactions of metal alkoxides in the presence of molecular assemblies of surfactants or related structure directing substances. [1±4] The original method, developed by scientists at Mobil Oil Research and Development, [1] has lead to extensive applications of these materials as catalyst supports and chromatographic resins. [4] The mechanism of organization of such a mesostructure involves electrostatic interactions and charge matching between micellar assemblies of quaternary ammonium cations (S + ) and anionic silicate oligomer species (I ± ).In many applications of mesoporous materials, functionalization of silanol groups on the surfaces of the materials are required. [5±7] Presently, extensive research is being conducted to develop procedures to introduce functional silane ligands into the surfaces of the ordered mesoporous materials. For example, Liu and coworkers [6] have recently developed new and more effective mesoporous sorbents for the removal of toxic metal ions by coating surfaces of the hexagonally packed mesoporous silica with organic functional groups to enhance the affinity of the mesoporous sorbents for toxic metal ions. Similar sorbents have also been described by Mercier and Pinnavaia. [7] The generally accepted mechanism for the direct coating method involves the initial hydrolysis of siloxane groups in the functional silane ligand followed by condensation with the surface silanol groups to produce ligands that are covalently bonded or ªtetheredº to the surfaces. Drawbacks associated with this direct coating method are: 1) the requirement of timeconsuming (>24 h) syntheses under reflux and 2) low loading of functional silane ligands. In this communication we _______________________ ± [*] Dr.

Self-Assembled Nanowire Networks by Deposition of Copper onto Layered-Crystal Surfaces

“…Condensation of Cu atoms in opening cracks, however, withdraws more electrons from the topmost triple-layer, which promotes further dilative stresses and, consequently, further cracking. According to previously published results, [9] an intercalation of atoms occurs to a finite penetration depth from the edges of the crystal. This model explains all experimental observations presented here as well as the behavior of Rb found in our earlier studies.…”

“…Besides the Cu clusters, the opening cracks act as further (and much more efficient) condensation points for Cu atoms. [9] In the wet chemical intercalation process metal ions from an electrolyte are intercalated in a layered crystal by applying an external voltage. At the end of this process, most of the deposited single Cu atoms are incorporated in nanowires, while a minor fraction remains agglomerated in Cu clusters between the wires.…”

“…[6] Various PF copolymers were synthesized with emission colors covering the entire visible spectrum [7,8] and the liquid crystalline nature of most of the PFs allows for specific orientations and thereby enables the realization of PLEDs generating polarized light emission. [9] One drawback of conjugated polymers in solid-state device applications is the quenching of luminescence by intermolecu-lar interactions, [10] chemical defects, [11] and excited states such as polarons. [12,13] In order to reduce these quenching effects the use of dendrimers was suggested.…”

Functionalized Mesoporous Silica via an Aminosilane Surfactant Ion Exchange Reaction: Controlled Scaffold Design and Nitric Oxide Release

“…We rationalized that this phenomenon might be due to an ion-exchange process between the surfactant and protonated aminosilanes ( Figure 6 ). Both Dai et al 61 and Bourlinos et al 62 have described ion exchange between cationic species (metal ions and aminosilanes, respectively) and the CTAB template as a method for particle modification. In both cases, the uncalcined (i.e., CTAB-containing) silica was modified in a separate reaction rather than a one-step procedure.…”

Adsorption and Thermogravimetric Characterization of Mesoporous Materials with Uniform Organic−Inorganic Frameworks

“…[18][19][20][21] Another important approach for the functionalization of silica OMMs is their surface modification with organic groups of desired functionality, typically with organosilanes. This can be achieved via chemical modification of surfactant-free 1,[22][23][24][25][26][27][28][29][30][31][32] or surfactant-containing OMMs 22,[33][34][35] and via direct synthesis of functionalized OMMs by cocondensation of siloxane and organosiloxane precursors. [36][37][38][39][40][41] All kinds of OMMs discussed above exhibit purely inorganic frameworks, which limits the ability to tailor their mechanical, chemical, and other properties.…”