Sulphonic acid functionalized periodic mesoporous organosilica with the bridged bissilylated urea groups for high selective adsorption of cobalt ion from artificial seawater

• We synthesized sulphonic acid functionalised N,N′-diureylenepyridine PMO.
• The organic moieties with sulphonic acid were produced in frameworks of pore walls.
• The material shows high selective adsorption (96.1%) of Co2+ from artificial seawater.
• The high selectivity was realized in the presence of various interfering metal ions.

Bissilylated urea-bridged periodic mesoporous organosilicas (DUP-PMOs) were synthesized by the co-condensation of N,N′-diureylenepyridine-bis-[(3-propyl)triethoxysilane)] (DUP) and tetraethyl orthosilicate (TEOS) using a triblock copolymer (Pluronic P123) as a structure-directing agent at various DUP to TEOS ratios. Sulphonic acid-functionalized PMOs (SUP-PMOs) were prepared based on a reaction between amine groups of DUP-PMO with chlorosulphonic acid in chloroform under mild reaction conditions. These PMOs were well characterized by small angle X-ray scattering, N2 adsorption–desorption measurements, Fourier-transform infrared spectroscopy, solid state 29Si magic angle spinning (MAS) and 13C cross polarisation-MAS nuclear magnetic resonance spectroscopy, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The DUP-PMOs and SUP-PMOs had an ordered mesostructure, high to low surface area (ranging from 637 to 38 m2 g−1), medium pore volume (0.69–0.05 cm3 g−1) and uniform pore sizes (4.3–5.2 nm). The functionalized PMOs were used effectively for the adsorption of Co2+ ions with high selectivity from artificial seawater. Owing to the presence of highly hydrophilic sulphonic acid moieties as pendent functional groups in the 1 and 3 positions of the urea nitrogen atoms, the materials were found to be highly suitable for the adsorption of Co2+ ions from artificial seawater at pH 8 with 96.1% selectivity, even in the presence of several interfering metal ions, such as Cr3+, Cu2+, Ni2+, and Li+. The adsorption experiments showed that the selectivity towards Co2+ depended heavily on the sulphonic acid loading on the surface nitrogen of diureylenepyridine-bridged PMO and the time of contact with metal ions in the artificial seawater.

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