Swollen and highly ordered MCM-41 type materials with varied pores sizes, but with similar wall thicknesses, have been directly synthesized in the absence of auxilliary organics by controlling the preparation conditions. The most important parameter in the synthesis in order to control the pore opening is the cetyltrimethylammonium (CTMA+) concentration in the synthesis gel. Our results suggest that the mechanism of swelling is related with the replacement of some CTMA+ species by others cations in the interface formed between the liquid crystal and the silica surfaces. This approach could open new insights into the mechanism of formation of MCM-41 type materials as well as having in addition an important impact on the preparation of large mesoporous materials.

No abstract

Transition metal (Fe 2+ , Co 2+ , VO 2+ or Cu 2+ ) Schiff base complexes were immobilized onto graphene oxide previously functionalized with 3-aminopropyltriethoxysilane (3-APTES). X-ray diffraction (XRD), IR spectroscopy, thermal gravimetric analyses (TGA) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) confirmed the successful incorporation of the metal Schiff base onto the graphene oxide. N 2 adsorption-desorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed the intact structure of the graphene oxide. Catalytic results showed that the immobilized copper(II) Schiff base complex catalyst was more active than the immobilized iron(II), cobalt(II) and oxovanadium(IV) complexes in the epooxidation of styrene. Above 94% styrene conversion and excellent $99% selectivity to the epoxide could be achieved over the copper(II) Schiff base heterogeneous catalyst in the epoxidation of styrene using tert-butyl hydroperoxide (TBHP) as oxidant after 7 h reaction. The recycling experiment results indicated that the catalyst could maintain very high styrene conversion (>93%) and epoxide selectivity (>99%) even after being used for four cycles.