Synthesis of ordered and disordered silicas with uniform pores on the border between micropore and mesopore regions using short double-chain surfactants

Determination and tailoring the pore entrance size in ordered silicas with cage-like mesoporous structures

A practical approach to the determination of the pore entrance size in ordered silicas with cage-like mesoporous structures (OSCMSs) is proposed. A fundamental insight into the OSCMS pore connectivity is gained, including the control of the pore entrance size by post-synthesis surface modification, and by selection of appropriate synthesis temperature. These findings show a new promise for the synthesis of mesoporous solids with molecular size- and shape-selective properties.

Novel bifunctional periodic mesoporous organosilicas, BPMOs: synthesis, characterization, properties and in-situ selective hydroboration-alcoholysis reactions of functional groups

A new class of bifunctional periodic mesoporous organosilicas (BPMOs) containing two differently bonded organic moieties in a mesoporous host has been synthesized and characterized. By incorporating bridge-bonded ethylene groups into the walls and terminally bonded vinyl groups protruding into the channel space, both the chemistry and physical properties of the resulting BPMO could be modified. The materials have periodic mesoporous structures in which the bridging ethylene plays a structural and mechanical role and the vinyl groups are readily accessible for chemical transformations. The vinyl groups in the material underwent hydroboration with BH(3).THF and the resulting organoborane in the BPMO was quantitatively transformed into an alcohol using either H(2)O(2)/NaOH or NaBO(3).4H(2)O. The materials retained ordered structures after subsequent in situ reactions with largely unchanged pore volumes, specific surface areas and pore size distributions. Other organic functionalized BPMO materials may be synthesized in a similar manner or by further functionalizing the resulting borylated or alcohol functionalized BPMO materials. The thermal properties of the BPMO materials have also been investigated and are compared to those of the periodic mesoporous organosilica (PMO) materials. Noteworthy thermal events concern intrachannel reactions between residual silanols or atmospheric oxygen and organics in BPMOs. They begin around 300 degrees C and smoothly interconvert bridging ethylene to terminal vinyl groups and terminal vinyl to gaseous ethene and ethane, ultimately producing periodic mesoporous silica at 900 degrees C that exhibits good structural order and a unit-cell size decreased relative to that of the parent BPMO.