Covalent Incorporation of Ethylenediamine Ligands in the Framework of Periodic Mesoporous Organosilica Nanostructure

Abstract

The covalent incorporation of ethylenediamine ligands in the framework of periodic mesoporous organosilica (PMO) nanostructure via mixed surfactants self-assembly process has been described. Propyl ethylenediamine group was employed to functionalize the pore channels of ethane-bridged PMO by co-condensation of 1,2-Bis(triethoxysilyl)ethane (BTSE) and (trimethoxysilyl)propyl]ethylenediamine (EDA-TES) in the presence of mixed surfactants (cetyltrimethylammonium bromide and fluorosurfactant (FSN100)) under basic conditions. In order to elucidate the effect of EDA-TES concentration on their mesoscopic organization and pore structure of the final PMO structures, the morphology of PMO nanostructures was investigated in detail by using X-ray diffraction (XRD), transmission electron microscopy (TEM), solid-state nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, and N2 adsorption. FTIR and NMR results have confirmed that ethane bridging groups in the final framework have not been cleaved and EDA-TES functions have been covalently anchored to the pore wall of PMO. The structural regularity of mesopore decreases with increasing concentration of EDA-TES in the initial mixtures except for the samples with 15 and 30 wt% EDA-TES concentrations, which exhibits a highly ordered two-dimensional hexagonal symmetry, supported by XRD patterns and TEM. Overall, the increase of EDA-TES contents results in the decreased surface area and total pore volume, indicating that the framework of PMO is covalently functionalized with EDA-TES function.