Macroporous periodic mesoporous organosilicas with diethylbenzene bridging groups

Periodic mesoporous organosilicas (PMOs) with diethylbenzene bridging groups (DEB) in the pore walls are promising adsorbents for harmful compounds including nitroenergetics. The hierarchical macropore–mesopore structures developed here are expected to facilitate diffusion for such applications and to offer the potential for application in column formats. DEB-functionalized PMOs were synthesized with triblock copolymer Pluronic®P123 and the swelling additive mesitylene. Many of the materials were prepared through co-condensation of the DEB precursor bis(trimethoxysilylethyl)benzene with 1,2-bis(trimethoxysilyl)ethane (BTE) to improve mesostructure. Conditions were optimized to form micron-scale macropores by polymerization-induced phase separation. PMOs were also produced using only the DEB precursor. These materials exhibited relatively high surface areas (ca. 400 m2/g) and mesopore sizes (ca. 45 Å) as well as isolated macropores. As-synthesized materials were fabricated as centimeter-scale monoliths that became powders after multiple solvent refluxes. Soxhlet extraction could be used to preserve monolithic morphology while removing enough P123 to access mesopores. Nitrogen sorption, powder X-ray diffraction, SEM, TEM, and TGA were applied to characterize the PMOs.