Fast synthesis of mesoporous silica materials via simple organic compounds templated sol–gel route in the absence of hydrogen bond

Abstract

As simple organic compounds that contain no hydroxyl, amino or carboxyl groups cannot assemble with the siliceous species through hydrogen bond or electrostatic force, they have not been applied as templates to prepare mesoporous silica materials before. However, in this work it was found that only if the organic compound can form homogeneous solution with ethanol and water can it successfully lead the formation of mesopores under the catalysis of 5% ammonium hydroxide (NH4OH) solution. The effects of template type, template amount and NH4OH solution concentration on the pore structure of the prepared porous silica were comprehensively studied. The pore size had no direct correlation with the molecular size of the template, but it could be easily adjusted in the range of 2.4–6.6 nm through changing the template amount. When using 5% NH4OH solution as the catalyst, the gelation time of siliceous species was ultrashort and therefore the template aggregates could be trapped in the three-dimensional SiO2 matrixes to function as the pore-forming agents. However, when the concentration of NH4OH solution was excessive high, like 15%, the gelation reaction was over intense and mesopores cannot be formed in the prepared silica. The mesoporous silica materials prepared in this new sol–gel route can be used as good supports of CO2 adsorbents. Through loading PEI into the mesopores of the silica materials, the solid amine adsorbents could be easily prepared, and they can keep remarkable CO2 adsorption ability even after 10 adsorption–desorption cycles.