TiO₂–SiO₂ Self-Standing Materials bearing Hierarchical Porosity: MUB-200(x) Series toward 3D-Efficient VOC Photoabatement Properties

Abstract

Three-dimensional photoactive self-standing porous materials have been synthesized through the integration of soft chemistry and colloids (emulsions, lyotrope mesophases, and P25 titania nanoparticles). Final multiscale porous ceramics bear 700–1000 m2 g–1 of micromesoporosity depending on the P25 nanoparticle contents. The applied thermal treatment does not affect the P25 anatase/rutile allotropic phase ratio. Photonic investigations correlated with the foams’ morphologies suggest that the larger amount of TiO2 that is introduced, the larger the walls’ density and the smaller the mean size of the void macroscopic diameters, with both effects inducing a reduction of the photon transport mean free path (l t) with the P25 content increase. A light penetration depth in the range of 6 mm is reached, thus depicting real 3D photonic scavenger behavior. The 3D photocatalytic properties of the MUB-200(x) series, studied in a dynamic “flow-through” configuration, show that the highest photoactivity (concentration of acetone ablated and concentration of CO2 formed) is obtained with the highest monolith height (volume) while providing an average of 75% mineralization. These experimental results validate the fact that these materials, bearing 3D photoactivity, are paving the path for air purification operating with self-standing porous monolith-type materials, which are much easier to handle than powders. As such, the photocatalytic systems can now be advantageously miniaturized, thereby offering indoor air treatment within vehicles/homes while drastically limiting the associated encumbrance. This volumetric counterintuitive acting mode for light-induced reactions may find other relevant advanced applications for photoinduced water splitting, solar fuel, and dye-sensitized solar cells while both optimizing photon scavenging and opening the path for the miniaturization of the processes where encumbrance or a foot-print penalty would be advantageously circumvented.

Hierarchical Porous WO3@SiO2 Self-Standing Monolithic Catalysts and Their Efficient Cycling “Cosolvent-Free” Friedel–Crafts Alkylation/Acylation Catalytic Properties

“…We notice that for the MUB-104­( x ) series, the materials’ hydration strength is strong, and we had a hard time drying the sample before He sorption. As such, repeatability induces a standard deviation of ±0.05, where generally a standard deviation of ±0.01 is proposed. − …”

“…Low Fick diffusion kinetics circumvented with the Taylor−Aris dispersive behavior occurring at the interfaces (vicinity) between the macroscopic walls and convecting/advecting fluids. We have demonstrated elsewhere 13,20 that beyond mass transport, photonic transport is also favored in the bulk of the catalysts (Mie scattering effect), harvesting photocatalysis in volume, thereby minimizing footprint penalty. High stability regarding the temperature and the solvents in use allows, beyond thermodynamic stability, ease of regeneration through a simple thermal or washing treatment.…”

“…15,16 Taking inspiration from this work, we developed novel binarymineral cellular materials, where transition metal cations substitute NH 4 + , such as niobium, 17 cobalt, 18 and copper, 19 or the salt is replaced with P25 Degussa nanoparticles. 20 As such, we have already prepared and characterized the niobium oxide Nb 2 O 5 −SiO 2 (HIPE), labeled as MUB-105(x) series, depicting good efficiency toward "cosolvent-free" Friedel− Crafts acylation and alkylation reactions. It is in this vein of acid-based heterogeneous catalysts that this article falls, depicting the first generation of WO 3 −SiO 2 self-sanding catalysts, named hereafter MUB-104(x) series, bearing hierarchical porosity addressing outstanding "cosolvent-free" alkylation/acylation catalytic properties.…”

“…Foremost, the drying procedure involves capillary forces that both induce cracks and restrain the monolithic self-standing character. However, SBA-15–Si­(HIPE) materials bearing a two-dimensional (2D) hexagonal mesoporous structure have been recently obtained while inducing an ammonium salt-based “order-maker” effect. , Taking inspiration from this work, we developed novel binary-mineral cellular materials, where transition metal cations substitute NH 4 + , such as niobium, cobalt, and copper, or the salt is replaced with P25 Degussa nanoparticles . As such, we have already prepared and characterized the niobium oxide Nb 2 O 5 –SiO 2 (HIPE), labeled as MUB-105­( x ) series, depicting good efficiency toward “cosolvent-free” Friedel–Crafts acylation and alkylation reactions.…”

Surface Structure Analysis and Formaldehyde Removal Mechanism of Lotus Shell Biochar: An Experimental and Theoretical Perspective

“…The increasing prevalence of air pollution-related diseases has heightened the awareness of volatile organic compounds (VOCs) as hazardous environmental pollutants, leading to a growing focus on their detrimental effects. − Formaldehyde (HCHO), a widespread VOC, is ubiquitously present in indoor air environments. , This colorless and flammable gas exudes a pungent and irritating odor and is widely used in the manufacture of resins, textiles, and other products. Recognized as a carcinogenic substance by the International Agency for Research on Cancer (IARC), HCHO has been linked to various adverse health impacts, including eye, nose, and throat irritation, respiratory difficulties, headaches, and allergic reactions. − Long-term exposure to HCHO can result in serious health consequences, including cancer.…”