Na2EDTA: Trifunctional controller for formation of tubular mesoporous silica at circumneutral pH and low temperature

Using organic salt Na2EDTA as trifunctional controller, hollow silica tubes with mesoporous wall were synthesized at circumneutral pH and low temperature. XRD, N2 sorption measurements, FTIR, TG-DTA, 29Si MAS NMR, SEM and TEM were performed to characterize the topology and morphology of mesoporous silica. The material exhibits disordered wormlike mesoporous structure with thick pore wall (estimated to be about 3 nm). The diameter of silica tubes ranges from 1 to 5 μm with the wall thickness of about 100–200 nm. Na2EDTA plays ternary roles in the synthesis: (1) as catalyst for hydrolysis and condensation of TEOS at circumneutral pH and low temperature; (2) to co-assemble with micelles of CTAB to give rise to wormlike mesoporous structure and (3) the incipient crystallization of Na2EDTA as template to induce formation of tubular morphology. The addition of ethanol to the synthesis system benefits the formation of silica tubules.