Single-template periodic mesoporous organosilica with organized bimodal mesoporosity

Abstract

Periodic mesoporous organosilicas (PMOs) are obtained by the hydrolysiscondensation of organobridged triethoxysilane precursors in the presence of surfactants as structure-directing agents (SDAs). After removal of the SDAs, the resulting materials usually exhibit monomodal, well-organized mesoporosity, with the size of the pores being controlled by the SDA. However, despite the potential technological applications of such materials with well-organized bimodal porosity, to the best of our knowledge, PMOs exhibiting two distinct types of ordered mesoporosity have barely been described.Herein, we describe a simple approach for modulating the dimensions of ordered monomodal 2D hexagonal and bimodal porosity in PMOs synthesized from 1,4-bis(triethoxysilyl)benzene (BTEB) and Pluronic P123 under acidic conditions, by varying the addition sequence of reactants. The approach employs a single SDA without degradation of the BTEB precursor. Reaction conditions leading to the formation of monomodal and bimodal porosity within the templated PMOs are identified. Our approach exploits the competition between the rates of (a) BTEB hydrolysis/condensation; and (b) diffusion, solubilization and partitioning of the unhydrolyzed and hydrolyzed precursor within the micelles. A mechanism describing the evolution of porosity within this system is proposed.

Newly Designed Mesoporous Silica and Organosilica Nanostructures Based on Pentablock Copolymer Templates in Weakly Acidic Media

“…The thermal stability of samples synthesized at high temperatures is also maintained. Higher stability of organosilica using boric acid catalyst has also been reported previously in other literature work [16,26,27].…”

“…An almost similar value of surface area is observed for the samples PMOBHs which suggests retention of mesoporosity during the synthesis at 40 • C temperature (Figure 9a). Narrow PSD is observed for all organosilica samples indicating considerable uniformity of mesostructures while a bimodal type PSD plot in case of silica samples (Figure 7b) suggests two types of pore diameters is observed in the sample [9,25,26]. The pore diameters measured at the maxima of the PSD plots (D KJS ) vary significantly from 2.8 to 9.5 nm for PMSA and PMSB silica samples, whereas a similar range of pore diameter (5.27-6.57 nm) is shown by organosilica samples.…”

Acetone Factor in the Design of Cu4-, Cu6-, and Cu9-Based Cage Coppersilsesquioxanes: Synthesis, Structural Features, and Catalytic Functionalization of Alkanes

“…Taking into attention the well-described affinity of trialkoxysilanes to form condensed derivatives (e.g., nanostructured materials and catalysts − ), a similar approach was chosen for the self-assembly of the target Cu­(II)-CLMS: alkaline (NaOH in ethanol) hydrolytic condensation of PhSi­(OMe) 3 , followed by an exchange reaction with CuCl 2 and complexation with ethylenediamine. Different reaction media were tested for the subsequent crystallization procedures (Scheme ).…”

Getting closer to the intrinsic properties of Ni2+salen polymer semiconductors accessed by chain isolation inside silica nanochannels

“…The calculated C/Ni ratio of 27 is more than the expected one (20), and the overvaluation probably originates from some remaining ethoxy groups in the mesoporous silica film. 62,63…”