Chemical modification and adsorption of the pure silica mesoporous molecular sieve KIT-1

The pure silica mesoporous molecular sieve (KIT-1) was chemically modified using both organic and inorganic precursors and characterized using FTIR, XRD, MAS NMR, TG-DSC and physical adsorption-desorption of nitrogen. Experimental results showed that the original mesoporous structure of the samples remained after modification. The IR and MAS NMR spectra demonstrated that the organic groups (-Si(CH3)(3) and -OCH2CH3) had successfully grafted onto the inter-surface of KIT-1 and inorganic atoms (Al, Si) attached at silicon atoms located in the hydrophobic part of the surface of KIT-1, but the grafted samples showed a lower BET surface area pore volume and smaller pore size. Modification using trimethylehlorosilane (TMCS) and TEOS was found to result in a significant loss in porosity. The surface property of samples was measured through adsorption capacity for the vapour of water or toluene. The modification samples show a higher adsorption capacity to toluene as compared to the parent KIT-1. The hydrophobicity of the sample modified by TMCS is much higher than other modified samples. Chemical modifications can greatly improve the hydrothermal stability of KIT-1 material because of the changed surface property.