Mesosynthesis of ZnO−Silica Composites for Methanol Nanocatalysis

Abstract

Methanol catalysis meets chemistry under confined conditions. Methanol is regarded as one of the most important future energy sources. ZnO/Cu composite materials are very effective in heterogeneous catalysis for methanol production due to the so-called strong metal-support interaction effect (SMSI). Therefore, materials of superior structural design potentially representing model systems for heterogeneous catalysis are highly desired. Ultimately, such materials could help to understand the interaction between copper and zinc oxide in more detail than currently possible. We report the preparation of nanocrystalline, size-selected ZnO inside the pore system of ordered mesoporous silica materials. A new, liquid precursor for ZnO is introduced. It is seen that the spatial confinement significantly influences the chemical properties of the precursor as well as determines a hierarchical architecture of the final ZnO/SiO 2 nanocomposites. Finally, the ability of the materials to act as model systems in methanol preparation is investigated. The materials are characterized by a variety of techniques including electron microscopy, X-ray scattering, solidstate NMR, EPR, EXAFS, and Raman spectroscopy, and physisorption analysis.

Preparation of High‐Surface‐Area Zinc Oxide with Ordered Porosity, Different Pore Sizes, and Nanocrystalline Walls

“…[16][17][18] The liquid ZnO-precursor [{H 3 CZnO-A C H T U N G T R E N N U N G (CH 2 ) 2 OCH 3 } 4 ] was prepared according to the literature. [8] The infiltration experiments were performed under exclusion of air and moisture by using Schlenk techniques, and the mesoporous carbon was carefully dried prior to use. Typically, 0.3 g of the mesoporous carbon powder was stratified with the liquid and undiluted [{H 3 CZnO-A C H T U N G T R E N N U N G (CH 2 ) 2 OCH 3 } 4 ].…”

“…[7] Recently, we were able to prepare size-selected ZnO particles in the pores of ordered mesoporous silica materials. [8] The key to success in this preparation was the use of an innovative, organometallic-precursor system resembling ZnO on a molecular scale. [8,9] Due to the potentially large surface area, the idea is very tempting that the nanoporous material itself is composed of a matrix material that is catalytically more relevant than silica.…”

“…[8] The key to success in this preparation was the use of an innovative, organometallic-precursor system resembling ZnO on a molecular scale. [8,9] Due to the potentially large surface area, the idea is very tempting that the nanoporous material itself is composed of a matrix material that is catalytically more relevant than silica. This approach is still rather unexplored, although some success in the synthesis of non-siliceous, ordered mesoporous materials has been made.…”

Cu/ZnO aggregates in siliceous mesoporous matrices: Development of a new model methanol synthesis catalyst

“…By embedding the catalytically active component into a well-defined superstructure (e.g., a hierarchically structured mesoporous matrix), it should be possible to simultaneously simplify and miniaturize the supported catalyst [14][15][16][17][18][19][20] and to utilize in the preparation the favorable effects of the spatially confined reaction conditions on the chemistry occurring in the porous solid [21]. However, this approach carries the risk of interference by the pore walls of the matrix.…”

Nanoarchitectonics for Mesoporous Materials

“…507 Polarz et al reported the preparation of nanocrystalline, size-selected ZnO inside the pore system of ordered mesoporous silica materials. 508 Highly defined materials containing nanocrystalline ZnO may be interesting as new model systems for methanol catalysis. Sen et al reported the templateassisted fabrication of magnetic mesoporous silicamagnetite nanocomposites 509 which are capable of binding DNA or eluting DNA, and also can be used to extract RNA from bacterial cells.…”