Macro–mesoporous silicas complex and the carbon replica

Abstract

Novel macroporous silicas with ordered mesoporous wall structures (~15 nm in pore size) have been synthesized by finely balancing the emulsification of the oil phase with the self-assembly of the amphiphilic block copolymers. The nanocasting method was used to produce hierarchically ordered macro-mesoporous carbon materials. These porous materials have potential applications in catalysis, sorption, separation, etc.Keywords: Hierarchy; Macro-mesoporous; Silica; Carbon; Emulsion; Hydrophobic-hydrophilic balance IntroductionSince the first report of self-assembled mesoporous silicas [1], great efforts have been made to construct inorganic hierarchical structures [2], especially materials with multimodal porosity [3], which is of great importance in the fields of controlled drug-delivery, catalysis, adsorption, and other energy-related applications. Various approaches have been invented for the fabrication of multimodal porous materials, which are well summarized in recent review papers [4,5]. Emulsion templating has been considered one of the most promising routes to produce macroporous materials with tunable pore sizes from 50 nm to a few micrometers [6]. The introduction of macroporosity into mesoporous materials by emulsion templating, however, was found to be far more difficult than expected [7]. For example, for the amphiphilic block copolymers involved emulsion systems [8], strong interactions between oil phase and amphiphilic block copolymers, especially when large amounts of oil (e.g., TMB) was used, often leads to the destruction of mesoscale ordering, forming a lamellar [9] or mesocellular foam (MCF) structures eventually [10]. On the other hand, systems with weaker oil-surfactant interactions are not easily emulsified. As a result, very large hollow spheres (a few micrometers in diameter) with mesoporous walls were obtained, in which high intrusion energy (high stir speed) was often involved [11]. In other works, vesicle structures [12], giant surfactant superstructures [13,14], even bubbles etc. have been used to assist in the construction of macro-mesoporous materials. Su et al. [14] have synthesized a set of hierarchically macro-mesoporous metal oxide in a single surfactant system, in which the templating of giant surfactant superstructures (from unreacted excess surfactant) is responsible for the formation of channel-like macropore systems. However, this approach does not work to prepare silica systems with similar porous structures [15]. To date, only hard template routes, such as colloidal crystals, have been successfully used in the construction of macro-mesoporous materials [4]. It remains a challenge to find a facile and efficient route to the fabrication of hierarchically ordered macro-mesostructures. Our previous studies show that different alkanes have different interactions with P123 amphiphilic block copolymer. By tuning the initial reaction temperatures and compositions of the synthetic mixture, control of inorganic-organic micelle arrangements may be achieved. As a result, mesopor...

Novel Mesoporous Silica Materials with Hierarchically Ordered Nanochannel: Synthesis with the Assistance of Straight-Chain Alkanes and Application

“…The mesoporous silica materials obtained in the straight-chain assisted system can be used as hard templates for the preparation of other mesoporous materials [104,105]. The assistance of -hexane leads to formation of a macromesoporous silica material, which was used as the hard template for the preparation of hierarchically ordered macromesoporous carbon materials [106].…”

Nano-casted N-Doped Carbon Created From a Task-Specific Protic Salt and Controlled Porous Glass

“…The obtained results demonstrated the applicability of commercially available CPG to produce carbon replica with a well-defined nanoarchitecture. Typical macroporous carbon replica reported in literature have macropores in the size range of 200 nm (Sun et al, 2007; Zhong et al, 2009; Prévot et al, 2011) up to a micrometer (Cai et al, 2006). The reported material with its median pore width being approximately 60 nm was found to be rare in reported literature apart from the work by Eisenberg et al (2016) which reported a median pore width slightly less than 50 nm for their N-doped hierarchical carbon.…”

A family of ordered mesoporous carbons derived from mesophase pitch using ordered mesoporous silicas as templates

“…In spite of extensive activity in this area, the use of large-pore SBA-15 (LP-SBA-15; pore diameter >12 nm) as a template has been nearly unexplored. To the best of our knowledge, only Sun et al (2007) applied macroporous-mesoporous LP-SBA-15 with d 100 interplanar spacing of ∼14 nm to synthesize an ordered mesoporous carbon (as seen from TEM) that retained the morphology of the template and exhibited narrow pore size distribution (pore diameter ∼6 nm). However, XRD or SAXS data were not reported, so the crucial information about the periodicity and unit-cell size is not available.…”

“…2(b), the carbon samples prepared at different infiltration temperatures had similar Type IV adsorption-desorption isotherms. The capillary condensation steps occurred in the relative pressure range from 0.45 to 0.65 and the isotherms leveled off at higher relative pressure, indicating uniform pore structures and low Sun et al (2007) for their macroporous-mesoporous carbon prepared using a similar template. However, these researchers did not report X-ray diffraction/scattering data, so overall periodicity of their carbon is not clear.…”