Diamine Groups on the Surface of Silica Particles as Complex-Forming Linkers for Metal Cations

Novel spherically shaped organosilica materials with (propyl)ethylenediamine groups were obtained via a modified one-pot Stober co-condensation method. The porosity of these materials was tuned with the controlled addition of three silica monomers acting as structuring agents (tetraethoxysilane and bridged silanes with ethylene and phenylene bridges). The morphologies and structures of the synthesized materials were studied by SEM, DRIFT spectroscopy, CHNS elemental analysis, low-temperature nitrogen adsorption-desorption, and electrokinetic potential measurements. Their sizes were in the range of 50 to 100 nm, depending on the amount of structuring silane used in the reaction. The degree of the particles' agglomeration determined the mesoporosity of the samples. The content of the (propyl)ethylenediamine groups was directly related with the amount of functional silane used in the reaction. The zeta potential measurements indicated the presence of silanol groups in bissilane-based samples, which added new active centers on the surface and reduced the activity of the amino groups. The static sorption capacities (SSCs) of the obtained samples towards Cu(II), Ni(II), and Eu(III) ions depended on the porosity of the samples and the spatial arrangement of the ethylenediamine groups; therefore, the SSC values were not always higher for the samples with the largest number of groups. The highest SSC values achieved were 1.8 mmol(Cu(II))/g (for ethylene-bridged samples), 0.83 mmol(Ni(II))/g (for phenylene-bridged samples), and 0.55 mmol(Eu(III))/g (for tetraethoxysilane-based samples).

Automated summary

Novel spherically shaped organosilica materials with (propyl)ethylenediamine groups were synthesized using a modified one-pot Stober co-condensation method. The porosity of these materials was controlled by adding different silica monomers as structuring agents. The synthesized materials exhibited different sizes and mesoporosity depending on the amount of structuring silane used. The sorption capacities towards Cu(II), Ni(II), and Eu(III) ions varied depending on the porosity and spatial arrangement of the ethylenediamine groups.