SYNTHESIS OF g-C3N4/METAL-SBA-15 COMPOSITE: STUDY OF THE INFLUENCE OF THE DIFFERENT METALS ANCHORED IN THE SUPPORT.

Abstract

Carbon nitride (g-C3N4) polymers have garnered considerable attention from the environmental and energy sectors due to their low cost, low toxicity, unique structural and physicochemical properties, and their high physical and chemical stability; they find application as catalysts, as electrodes, as optoelectronic materials, etc. These materials primarily composed of carbon and nitrogen can be synthesized using various methods, but thermal polymerization employing low-cost raw materials containing carbon and nitrogen predominates. This study synthesized g-C3N4 supported Metal-SBA-15 mesoporous materials by evaluating the effect of metal on g-C3N4 formation. Carbon nitrides were synthesized using urea through the thermal polymerization method. Various supported carbon nitrides on mesoporous materials from the Si-based SBA-15 family were prepared. Additionally, a series of materials containing Ga, Al, Sn, and Zr anchored on SBA-15 (with Si/Metal ratio of 20) were tested. The attained g-C3N4/Metal-SBA-15 composites were characterized by XRD, ICP, EA, HR-TEM, SEM-EDX, and N2 adsorption isotherms, among others. To explore the chemical structure of the composites, the chemical bonds existing within the g-C3N4 structure were investigated by FT-IR spectroscopy. The FT-IR spectra of g-C3N4 samples, displayed characteristic peaks at 810 cm-1, 1410 cm-1, 1645 cm-1, and 3100– 3300 cm-1, which describe bending modes characteristic of the out-of-plane tri-units of triazine and C=N, stretching vibrations typical of the C=N and C–N bonds of aromatic CN heterocycles, and the stretching mode of the N‒H bond of non-condensed terminal amino groups, respectively. While SBA-15 material without metal did not exhibit absorption bands characteristic of a g-C3N4, Ga-SBA-15 and Zr-SBA-15 materials exhibited weak absorption bands in the region of 1100 and 1700 cm-1. Interestingly, materials containing aluminum and tin not only exhibited the characteristic bands of SBA-15 but also added the typical bands of g-C3N4. These results, also confirmed by other analysis, revealed that the g-C3N4 chemical structure was efficiently supported onto the metal-containing mesoporous materials. To complete the study, carbon nitride materials were attempted to be synthesized with sulfated zirconia/SBA-15 at different Si/Metal ratios. The results obtained were promising, thus allowing proving the positive effect of S species on the g-C3N4 formation.