Characterisation of Silica Extracted from Rice Husk Functionalised by Guanine (RHACGua)

Abstract

This study seeks to answer how the incorporation of guanine affects the structural properties and catalytic behaviour of the silica support. This study presents the characterisation of an organic-inorganic hybrid catalyst, named as RHACGua, derived from silica extracted from rice husk (RH). The catalyst was developed by incorporating guanine onto rice husk ash (RHA)-supported silica, utilising (3-chloropropyl) triethoxysilane (CPTES) as an anchoring agent to facilitate the binding of guanine to the silica. Characterisation of RHACGua was performed using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), powder x-ray diffraction (XRD), nitrogen sorption analysis, and solid-state nuclear magnetic resonance (NMR) spectroscopy for 29Si and 13C. SEM, XRD, and nitrogen sorption analyses revealed that RHACGua possesses a porous agglomerate structure with a specific surface area of 77.67 m²/g and a pore diameter of 15.81 nm. FTIR spectra demonstrated a shift in the Si-OSi band from 1038 cm^-1 in the precursor RHACCl to 1042 cm^-1 in RHACGua, confirming the successful incorporation of guanine and the presence of all expected functional groups. MAS NMR spectroscopy identified distinct silicon environments (Q4, Q3, T3, T2) in RHACGua, indicating effective modification of the Cl functional group with guanine. These findings confirm that the RHACGua catalyst was successfully synthesised via the modification of RHACCl with guanine, showcasing its potential for use in heterogeneous catalysis.