MCM-41

About: MCM-41 is a research topic. Over the lifetime, 2355 publications have been published within this topic receiving 91416 citations.

Ordered mesoporous MCM-41 silicon oxynitride solid base materials with high nitrogen content: synthesis, characterisation and catalytic evaluation

Abstract: We present here the synthesis, physicochemical characterisation and catalytic evaluation of mesoporous silicon oxynitride materials. The solid base catalytic materials were prepared by subjecting pure silica MCM-41 mesoporous molecular sieves to nitridation, i.e., treatment with ammonia at high temperature. The mesoporous MCM-41 silicon oxynitride materials are well ordered and possess high surface area and pore volume. The nitrogen content was controlled within the range 8.6 to 25.1 wt% by simply changing the nitridation temperatures (between 850 and 1150 °C) or the time allowed for nitridation (from 20 to 80 hours). The nitrogen is incorporated onto the MCM-41 framework in the form of various NHx species, including terminal NH2 and bridging NH groups as well as adsorbed ammonium ions. The oxynitride materials were found to exhibit considerable catalytic activity for the Knoevenagel condensation reaction. The catalytic activity was correlated to the nitrogen content and was therefore highest for materials nitrided at high (1150 °C) temperature. In all cases, the nitrided materials were found to be generally stable with respect to storage and they suffered no significant structural degradation over a period of a few months. Oxynitride materials with the highest nitrogen content (i.e., those nitrided at temperatures ≥1050 °C) were found to be more susceptible to loss of surface area and pore volume after storage under ambient conditions for 6 months. The ease of preparation and control of the nitrogen content of mesoporous oxynitride materials and their stability makes them attractive as alternative solid base catalysts especially for large molecule transformations.

Adsorptive removal and kinetics of methylene blue from aqueous solution using NiO/MCM-41 composite

Abstract: Highly ordered mesoporous material MCM-41 was synthesized from tetraethylorthosilicate (TEOS) as Si source and cetyltrimethylammonium bromide (CTAB) as template. Well-dispersed NiO nanoparticles were introduced into the highly ordered mesoporous MCM-41 by chemical precipitation method to prepare the highly ordered mesoporous NiO/MCM-41 composite. X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and high-resolution TEM (HRTEM), and nitrogen adsorption–desorption measurement were used to examine the morphology and the microstructure of the obtained composite. The morphological study clearly revealed that the synthesized NiO/MCM-41 composite has a highly ordered mesoporous structure with a specific surface area of 435.9 m2 g−1. A possible formation mechanism is preliminary proposed for the formation of the nanostructure. The adsorption performance of NiO/MCM-41 composite as an adsorbent was further demonstrated in the removal azo dyes of methyl orange (MO), Congo red (CR), methylene blue (MB) and rhodaming B (RB) under visible light irradiation and dark, respectively. The kinetics and mechanism of removal methylene blue were studied. The results show that NiO/MCM-41 composite has a good removal capacity for organic pollutant MB from the wastewater under the room temperature. Compared with MCM-41 and NiO nanoparticles, 54.2% and 100% higher removal rate were obtained by the NiO/MCM-41 composite.

Hybrid Materials and Periodic Mesoporous Organosilicas Containing Covalently Bonded Organic Anion and Cation Featuring MCM-41 and SBA-15 Structure

Abstract: We report the synthesis of a new trialkoxysilylated ionic liquid based on disilylated guanidinium and monosilylated sulfonimide species. This compound allowed the successful preparation of new periodic mesoporous organosilicas containing covalently anchored ion-pair through both organo-cationic and organo-anionic moieties which have never been reported up to now. Two classes of hybrid materials containing guanidinium-sulfonimide ion-pairs (IPs) have been synthesized. The first type of material was prepared by grafting the silylated IP onto both MCM-41-type and SBA-15-type silicas according to a surface sol-gel polymerization. The second class was synthesized following a one-pot sol-gel procedure using silylated IP and tetraethoxysilane as framework precursors. These latter materials correspond to so-called periodic mesoporous organosilicas (PMOs) and gave "organo-ionically" modified MCM-41 and SBA-15 related solids. The materials were characterized by a series of techniques including XRD, nitrogen sorption, solid-state NMR, FTIR, transmission electronic microscopy, and elemental analysis. The highest structural regularity in terms of pore size distribution and channel size homogeneity was observed for IP-PMOs possessing SBA-15-type architecture due to an enhanced trialkoxysilylated IP precursor/surfactant interaction. Solvatochromic experiments with Reichardt's dye showed good accessibility of the silica-supported ion-pair and suggested the formation of monophasic materials.