Synthesis and properties of COK‐12 large‐pore mesocellular silica foam

Abstract

Large, ink-bottle-shaped pores in mesocellular foams (MCFs) are desired for various applications requiring enhanced mass transfer or the immobilization of larger compounds. Hence, the cylindrical pores of COK-12, an ordered mesoporous silica structurally comparable to SBA-15 but synthesized at roomtemperature at quasi-neutral pH, are chemically swollen into ink-bottle pores. Therefore, p-xylene is used as a more sustainable swelling agent compared to popular alternatives. Its high boiling point allows for an additional thermal aging step to amplify the mesostructure enlargement without needing additional chemicals. For COK-12, the MCFs obtained at room temperature reach an unprecedented plateau for the modal mesopore cell and window diameter of 19.9 and 5.5 nm, respectively, with an underlying broad pore size distribution and distorted hexagonal lattice up to 14.5 nm, involving hexagonal and spherical structures. The combined chemical and thermal swelling resulted in the selective enlargement of the window diameter to more than 200% and a slightly increased cell diameter, pore size distribution, and hexagonal lattice distortion in comparison to the room temperature synthesis. Such materials are thought to be promising alternatives to SBA-15-based MCFs, often utilizing toxic catalysts during synthesis. The presented results pave the way for enhanced adsorptive, catalytic, and drug delivery performances for COK-12-based materials.

Exploring 2D hexagonal WO3/COK-12 nanostructures for efficient humidity detection

“…These align with lattice planes (001), ( 111), ( 220), ( 201), ( 221) and ( 040), respectively, corresponding to the distinct planes of WO 3 (JCPDS 20-1324). 21,22 It can be seen that the amorphous peak at 221 is getting somewhat narrower, which can be attributed to the crystalline phase introduced by the presence of WO 3 in the material. The associated diffraction peaks are of low intensity due to the high dispersion of tungsten on 2D hexagonal COK-12 support.…”

Robocasting of ordered mesoporous silica‐based monoliths: Rheological, textural, and mechanical characterization

“…[56,57] Fitting of the SAXS data was performed using the SASfit software package, utilizing a previously reported fitting model for COK-12 samples. [42,44,58] The data collected on NaBent was modeled using a spherical formfactor alongside a flat background contribution and a Porod slope. NB-COK-X-M samples were modeled using a combination of both aforementioned models to account for contribution arising for both structures.…”

“…Furthermore, COK-12 requires only citric acid and its sodium salt as pH regulators, and while it still requires the use of a petroleum-derived soft-template, the entire synthesis can be carried out in water at room temperature (RT) and ambient pressure. Our group has previously reported on the modification, [39][40][41][42] upscaling, [38,43] and shaping [44] as well as the application [45,46] of COK-12. Additionally, a number of other groups have utilized COK-12 for different purposes.…”

“…[44] These methods are, however, not easily applicable to a monolith with a complex structure. To avoid high sintering temperatures and thus loss of mesoporosity [42,44,39] a low-cost, widely used, and sustainable inorganic binder, sodium bentonite (NaBent), is used to lower the processing temperature and diminish the loss of these useful properties of similar OMS (i.e., in AM. This binder was also explored in additively manufactured aminosilica monoliths in the context of gas adsorption and surface modification.…”