Hollow @CuMgAl double layered hydrotalcites and mixed oxides with tunable textural and structural properties, and thus enhanced NH3-NOx-SCR activity.

Well-organized, spherical, mesoporous hollow @CuMgAl-LDHs (layered double hydroxides) are prepared by the controlled removal of the SiO2 from SiO2@CuMgAl-LDH core-shell hybrids that in turn are synthesized via a bottom-up strategy. The materials are prepared with various Cu/Mg molar ratios (Cu/Mg = 0.05-0.50) while keeping the ratio of Cu and Mg constant, (Cu + Mg)/Al = 2. The effect of Cu doping and the silica core removal process (conducted for 4 h at 30 °C using 1 M NaOH) on the chemical composition, morphology, structure, texture and reducibility of the resulting materials are described. @CuMgAl-MOs (mixed oxides) obtained by thermal treatment of the @CuMgAl-LDHs are active and selective catalysts for the selective catalytic reduction of NOx using ammonia, and effectively operate at low temperatures. The N2 yield increases with increased Cu content in the CuMgAl shell, which is associated with the easier reducibility of the Cu species incorporated into the MgAl matrix. @CuMgAl-MOs show better catalytic performance than bulk CuMgAl MOs.

Reconstruction of the ZnAl Mixed Oxides Into the Layered Double Hydroxide Catalysts Active in the Aldol Condensation of Furfural: The Role of ZnO Particles.

A memory effect is the ability to restore the original, lamellar layered double hydroxide structure. Herein, we have described 1) the changes in the structural and basic properties of ZnAl mixed oxides during their transformation into ZnAl-reconstructed LDHs (RE-LDHs); 2) the extraordinary properties of ZnAl RE-LDHs compared to the original ZnAl LDHs; and 3) the changes of basic properties during the interaction of ZnAl RE-LDHs with atmospheric CO2. Aldol condensation was selected as probe reaction to prove the catalytic potential of ZnAl RE-LDHs. We have described a target method for preparing ZnAl RE-LDHs with a large number of basic sites. ZnAl RE-LDHs possess significantly higher furfural conversion in the aldol condensation of furfural than MOs. The structural, textural, and basic properties of the studied materials were described by temperature-programmed analysis, X-ray diffraction, N2 adsorption, temperature-programmed desorption of CO2, and in-situ diffuse reflectance spectroscopy.