Hierarchically porous and mechanically stable monoliths from ordered mesoporous silica and their water filtration potential

Abstract

Mechanically stable structures with interconnected hierarchical porosity combine the benefits of both small and large pores, such as high surface area, pore volume, and good mass transport capabilities. Hence, lightweight...

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

“…[ 10,29,30 ] Furthermore, the upscaling of the synthesis by a factor of five might have slightly contributed to broadening of the pore diameter toward larger values as indicated from COK‐12 pore sizes obtained from batches upscaled by the factors 25 and 50, respectively. [ 9,12 ] In accordance with the larger mesopores of COK‐12‐X0.5+A, the pore volume and SSA increase up to 640 m 2 g −1 and 1.55 cm 3 g −1 , while the micropore volume remains at about 50% of the micropore volume of COK‐12‐X0 and COK‐12‐X0.5. The enhanced pore swelling and loss of microporosity due to aging at 90°C, despite the smaller p ‐xylene concentration, can be ascribed to two phenomena: On the one hand, the p ‐xylene undergoes thermal expansion with increasing temperature.…”

“…The slight deviation at low p ‐xylene concentrations is likely to be attributed to the lower sensitivity of the NLDFT method in comparison to SAXS, as previously reported. [ 12 ] For COK‐12‐X0.5+A, the deviation of the SAXS window sizes toward the ones obtained by NLDFT is substantial with differences up to 5.7 nm, which might likely be attributed to the disruption of the remaining hexagonal pore structure, hampering the fitting process of NLDFT, employing highly ordered structures, and possibly also to a small fraction of inaccessible pores. Besides the change in the mesopore window sizes, a decrease in the intensity of the volume‐weighted distribution of the mesopore windows can be observed from the SAXS data with increasing p ‐xylene content and temperature, see Figure S6, along with a broadening of the distribution, similar to the observed micropore development.…”

“…[40,41] Fitting of the SAXS data was performed using a previously reported SAXS fitting model with some additions to better describe the swollen and ink-bottle shaped pores. [12] In short, fitting of the SAXS data was performed using SASfit, [42] allowing for information on the lattice parameter, macro-/ meso-/ and micropore sizes, alongside an additional spherical contribution, and in some cases, a second hexagonal contribution, to account for the spherical cells with ink-bottle shaped pores and enlarged window sizes of the thermally swollen COK-12-X0.5+A. More detailed information on the SAXS modelling can be found in the SI (Figures S1-S3).…”

“…[11] Finally, due to the overall ease of the COK-12 synthesis, successes toward upscaled and continuous procedures have been reported. [7,9,12] In general, by using a surfactant-templated synthesis route, the OMS mesostructure (e.g., hexagonal, lamellar, cubic, disordered), morphology (e.g., spheres, rods, crystals), and size (in the micro-, meso, and/or macropore range) can be tailored by controlling the synthesis conditions such as surfactant composition and concentration, temperature, pH, and through the choice of additives. [13] Driven by the vast development potential of OMS, siliceous mesocellular foams (MCFs) were first reported on in 1999.…”

“…[ 11 ] Finally, due to the overall ease of the COK‐12 synthesis, successes toward upscaled and continuous procedures have been reported. [ 7,9,12 ]…”