Synthesis of mesoporous silica using urea–formaldehyde resin as an active template

Urea (U)–formaldehyde (F) resin was prepared and used as an active template under acid and ethanol/water cosolvent conditions for synthesis of mesoporous silica, in which tetraethyl orthosilicate (TEOS) acts as the source of silica. The resin–silica composite particles and the gel product were achieved simultaneously in the procedure. The particle product with network structure was observed as the synthesis was performed in the initial F/U molar ratio region from 0.00 to 2.00, where the most amount of particles was yielded at the initial F/U molar ratio of 1.00. Synthesis performed at a high resin concentration with the initial F/U molar ratio of 3.00 yielded micron composite spheres as well. Although gel product could be obtained under all reaction conditions, the calcined gel product with controllable mesopore size and worm-like morphology was achieved only as the initial F/U molar ratio in preparation is above 1.00. Two model processes, i.e., continued deposition of monomers and cross-linking agglomeration between rigid resin cores were used in discussion of the synthesis mechanism.