Control of plugging in bifunctional periodic mesoporous organosilica with imidazolium framework (BFPMO) via stepwise addition of silica precursors

Abstract

Novel ordered two-dimensional (2D) hexagonal plugged and non-plugged bifunctional periodic mesoporous organosilicas (BFPMO) with variable content of bridged IL-phenyl or -ethyl units have been prepared using Pluronic P123 as a supramolecular structure directing agent (SDA) in acidic media. The final solvent extracted BFPMOs have been characterized by N₂ adsorption–desorption analysis, transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), thermal gravimetric analysis (TGA), ²⁹Si and ¹³C cross-polarization magic angle spinning (CP-MAS) NMR spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), scanning electron microscope (SEM) and elemental analysis. In particular, the CP-MAS NMR, DRIFT, and elemental analysis show that the functional groups were unchanged, without any Si–C bond cleavage in the BFPMO framework during the synthesis and even after surfactant extraction. The extent of plugging in the materials was, as expected, a function of both the hydrolysis rate of the silica and organosilica precursors, as well as the initial methanol concentration. However, for the first time, it was also found that the plugging could be also controlled via the stepwise addition of the silica precursors.