Syntheses of diethylenetriamine-bridged polysilsesquioxanes and their structure–adsorption properties for Hg(II) and Ag(I)

• DETA-bridged polysilsesquioxanes with soft long-chain organic bridge were obtained.
• CTAB and TEOS were used to avoid collapsing of pores.
• DETA-BPS with both high surface area and high functionalities were achieved.
• The adsorbents show high adsorption capacities for Hg(II) and Ag(I).

In this paper, a series of novel adsorbents, diethylenetriamine-bridged polysilsesquioxanes (DETA-BPS), were synthesized by sol–gel polymerization of prepared diethylenetriamine-bridged monomer containing soft long-chain organic bridge. Fully hydrolyzable silane tetraethylorthosilicate (TEOS), and porogen hexadecyl trimethyl ammonium bromide (CTAB), were used in the co-condensation process to help the construction of the porous framework of DETA-BPS materials. TEOS was found necessary in the framework construction. The addition of CTAB could increase the porosity significantly. The resulting materials have a porous structure (SBET in the range 58–438 m2 g−1) and a high content of functional groups (1.5–3.9 mmol g−1). The adsorption for Hg(II) and Ag(I) of the materials were studied. The results showed that different structures of DETA-BPS materials led to different adsorption capability to metal ions. Generally, the adsorption capacities for Hg(II) and Ag(I) of DETA-BPS with CTAB template were all higher than those without CTAB, even they had no ordered meso-structural framework. The DETA-BPS with higher content of functional groups showed higher adsorption capacity for Ag(I), while those with higher porosity showed higher adsorption capacity for Hg(II). The results provided valuable references for the applications of the DETA-BPS material as metal ion adsorbents.