Dihydrogen, methane, and carbon dioxide isotherm measurements were performed at 1−85 bar and 77−298 K on the evacuated forms of seven porous covalent organic frameworks (COFs). The uptake behavior and capacity of the COFs is best described by classifying them into three groups based on their structural dimensions and corresponding pore sizes. Group 1 consists of 2D structures with 1D small pores (9 A for each of COF-1 and COF-6), group 2 includes 2D structures with large 1D pores (27, 16, and 32 A for COF-5, COF-8, and COF-10, respectively), and group 3 is comprised of 3D structures with 3D medium-sized pores (12 A for each of COF-102 and COF-103). Group 3 COFs outperform group 1 and 2 COFs, and rival the best metal−organic frameworks and other porous materials in their uptake capacities. This is exemplified by the excess gas uptake of COF-102 at 35 bar (72 mg g−1 at 77 K for hydrogen, 187 mg g−1 at 298 K for methane, and 1180 mg g−1 at 298 K for carbon dioxide), which is similar to the performance of COF...

http://yaghi.berkeley.edu/pdfPublications/Furukawa09.pdf

Storage of Hydrogen, Methane, and Carbon Dioxide in Highly Porous Covalent Organic Frameworks for Clean Energy Applications

Because of their availability, adjustable microstructure, varieties of forms, and large specific surface area, porous carbon materials are of increasing interest for use in hydrogen storage adsorbents and electrode materials in supercapacitors and lithium–sulfur cells from the viewpoint of social sustainability and environmental friendliness. Therefore, much effort has been made to synthesize and tailor the microstructures of porous carbon materials via various activation procedures (physical and chemical activation). In particular, the chemical activation of various carbon sources using KOH as the activating reagent is very promising because of its lower activation temperature and higher yields, and well-defined micropore size distribution and ultrahigh specific surface area up to 3000 m2 g−1 of the resulting porous carbons. In this feature article, we will cover recent research progress since 2007 on the synthesis of KOH-activated carbons for hydrogen and electrical energy storage (supercapacitors and lithium–sulfur batteries). The textural properties and surface chemistry of KOH-activated carbons depend on not only the synthesis parameters, but also different carbon sources employed including fossil/biomass-derived materials, synthetic organic polymers, and various nanostructured carbons (e.g. carbon nanotubes, carbon nanofibers, carbon aerogels, carbide-derived carbons, graphene, etc.). Following the introduction to KOH activation mechanisms and processing technologies, the characteristics and performance of KOH-activated carbons as well as their relationships are summarized and discussed through the extensive analysis of the literature based on different energy storage systems.

KOH activation of carbon-based materials for energy storage

Three-dimensional covalent organic frameworks (3D COFs) were synthesized by targeting two nets based on triangular and tetrahedral nodes: ctn and bor. The respective 3D COFs were synthesized as crystalline solids by condensation reactions of tetrahedral tetra(4-dihydroxyborylphenyl) methane or tetra(4-dihydroxyborylphenyl)silane and by co-condensation of triangular 2,3,6,7,10,11-hexahydroxytriphenylene. Because these materials are entirely constructed from strong covalent bonds (C-C, C-O, C-B, and B-O), they have high thermal stabilities (400° to 500°C), and they also have high surface areas (3472 and 4210 square meters per gram for COF-102 and COF-103, respectively) and extremely low densities (0.17 grams per cubic centimeter).

http://science.sciencemag.org/content/sci/316/5822/268.full.pdf

Designed synthesis of 3D covalent organic frameworks.

Porous carbons have several advantageous properties with respect to their use in energy applications that require constrained space such as in electrode materials for supercapacitors and as solid state hydrogen stores. The attractive properties of porous carbons include, ready abundance, chemical and thermal stability, ease of processability and low framework density. Activated carbons, which are perhaps the most explored class of porous carbons, have been traditionally employed as catalyst supports or adsorbents, but lately they are increasingly being used or find potential applications in the fabrication of supercapacitors and as hydrogen storage materials. This manuscript presents the state-of-the-art with respect to the preparation of activated carbons, with emphasis on the more interesting recent developments that allow better control or maximization of porosity, the use of cheap and readily available precursors and tailoring of morphology. This review will show that the renewed interest in the synthesis of activated carbons is matched by intensive investigations into their use in supercapacitors, where they remain the electrode materials of choice. We will also show that activated carbons have been extensively studied as hydrogen storage materials and remain a strong candidate in the search for porous materials that may enable the so-called Hydrogen Economy, wherein hydrogen is used as an energy carrier. The use of activated carbons as energy materials has in the recent past and is currently experiencing rapid growth, and this review aims to present the more significant advances.

/pdf/energy-storage-applications-of-activated-carbons-2ct4qm4ni4.pdf

Energy storage applications of activated carbons: supercapacitors and hydrogen storage

In this work, with a zeolite-type metal-organic framework as both a precursor and a template and furfuryl alcohol as a second precursor, nanoporous carbon material has been prepared with an unexpectedly high surface area (3405 m(2)/g, BET method) and considerable hydrogen storage capacity (2.77 wt % at 77 K and 1 atm) as well as good electrochemical properties as an electrode material for electric double layer capacitors. The pore structure and surface area of the resultant carbon materials can be tuned simply by changing the calcination temperature.

/pdf/from-metal-organic-framework-to-nanoporous-carbon-toward-a-3p67kvclap.pdf

S. Saadallah

Papers

Hydrogen storage in activated carbon materials: Role of the nanoporous texture