"Space—the final frontier." This preamble to a well-known television series captures the challenge encountered not only in space travel adventures, but also in the field of porous materials, which aims to control the size, shape and uniformity of the porous space and the atoms and molecules that define it. The past decade has seen significant advances in the ability to fabricate new porous solids with ordered structures from a wide range of different materials. This has resulted in materials with unusual properties and broadened their application range beyond the traditional use as catalysts and adsorbents. In fact, porous materials now seem set to contribute to developments in areas ranging from microelectronics to medical diagnosis.

Ordered porous materials for emerging applications

Carbon materials for the electrochemical storage of energy in capacitors

Unilamellar colloids of graphite oxide (GO) were prepared from natural graphite and were grown as monolayer and multilayer thin films on cationic surfaces by electrostatic self-assembly. The multilayer films were grown by alternate adsorption of anionic GO sheets and cationic poly(allylamine hydrochloride) (PAH). The monolayer films consisted of 11−14 A thick GO sheets, with lateral dimensions between 150 nm and 9 μm. Silicon substrates primed with amine monolayers gave partial GO monolayers, but surfaces primed with Al13O4(OH)24(H2O)127+ ions gave densely tiled films that covered approximately 90% of the surface. When alkaline GO colloids were used, the monolayer assembly process selected the largest sheets (from 900 nm to 9 μm) from the suspension. In this case, many of the flexible sheets appeared folded in AFM images. Multilayer (GO/PAH)n films were invariably thicker than expected from the individual thicknesses of the sheets and the polymer monolayers, and this behavior is also attributed to folding...

http://dns2.asia.edu.tw/~ysho/YSHO-English/1000%20WC/PDF/Che%20Mat11,%20771.pdf

Layer-by-Layer Assembly of Ultrathin Composite Films from Micron-Sized Graphite Oxide Sheets and Polycations

The synthesis of massive arrays of monodispersed carbon nanotubes that are self-oriented on patterned porous silicon and plain silicon substrates is reported. The approach involves chemical vapor deposition, catalytic particle size control by substrate design, nanotube positioning by patterning, and nanotube self-assembly for orientation. The mechanisms of nanotube growth and self-orientation are elucidated. The well-ordered nanotubes can be used as electron field emission arrays. Scaling up of the synthesis process should be entirely compatible with the existing semiconductor processes, and should allow the development of nanotube devices integrated into silicon technology.

https://science.sciencemag.org/content/sci/283/5401/512.full.pdf

Self-Oriented Regular Arrays of Carbon Nanotubes and Their Field Emission Properties

http://staff.ulsu.ru/moliver/ref/polymers/pott11.pdf

Graphene-based polymer nanocomposites

An attempt was made to prepare porous carbon by using the channels of Y zeolite as a template. Poly(acrylonitrile) and poly(furfuryl alcohol) were carbonized in the zeolite channels and the resultant carbon/zeolite complexes were subjected to acid treatment in order to extract carbon from the zeolite framework. In addition, pyrolytic carbon deposition in the channels was carried out by exposing the zeolite to propylene at high temperature, and then the carbon was liberated in the same manner as above. The morphology and structure of the carbon prepared in the channels were characterized, and the results were discussed in relation to the morphology and structure of the original zeolite template. It was found that the microscopic morphology of the resultant carbons reflects that of the corresponding zeolites. All of these carbons are highly porous, and some of the CVD carbons have BET surface areas as high as >2000 m2/g.

Formation of New Type of Porous Carbon by Carbonization in Zeolite Nanochannels

A template carbonization technique was applied to prepare carbon nanotubes and submicron-tubes in one dimensional channels. An anodic aluminum oxide film that has uniform and straight channels with a diameter at the nanometer level was used as a one-dimensional template. The pyrolytic carbon deposition on the channel wall was carried out by exposing the anodic oxide film to propylene at 800 °C. The carbon was then liberated from the anodic oxide film by HF washing. It was found that the resultant carbon is comprised only of uniform hollow tubes with open ends. The infiltration of poly(furfuryl alcohol) into the channels of the film followed by heat treatment led to the formation of bamboolike carbon tubes. For all the carbon tubes obtained here, the outer diameter (30 or 230 nm) and the length (60 or 75 μm) precisely reflect the channel diameter and the thickness of the template used, respectively. Furthermore, in the case of the carbon tubes from propylene, the wall thickness of the tubes was easily cont...

Preparation of Ultrafine Carbon Tubes in Nanochannels of an Anodic Aluminum Oxide Film

Template synthesis of novel porous carbons using various types of zeolites

Preparation of a high surface area microporous carbon having the structural regularity of Y zeolite

By using zeolite Y as a template, a novel microporous carbon with a three-dimensional nano-array structure was prepared. The arrangement and periodicity of this array are identical to those of supercages in zeolite Y crystal. The carbon has a surprisingly high BET surface area (3600 m2/g) with almost no mesoporosity. This carbon may be comprised of very curved graphene sheets whose faceting and curvature are accommodated to the curved inner surface of the zeolite nanochannels.

Akira Tomita

Papers

Formation of New Type of Porous Carbon by Carbonization in Zeolite Nanochannels

Preparation of Ultrafine Carbon Tubes in Nanochannels of an Anodic Aluminum Oxide Film

Template synthesis of novel porous carbons using various types of zeolites

Preparation of a high surface area microporous carbon having the structural regularity of Y zeolite

Very High Surface Area Microporous Carbon with a Three-Dimensional Nano-Array Structure: Synthesis and Its Molecular Structure