Surface covalent organic frameworks

Very recently covalent organic frameworks (COFs) 33 have been designed and synthesized by simply condensation of phenyl diboronic acid with hexahy-droxytriphenylene (67) (Fig. 14). Material 33 is composed of expanded porous graphitic layers, with pore sizes up to 27 A. Covalent organic framework (33) is thermally stable till 500-600°C and have a surface area of 1590 m g. This exceeds the highest reported surface area of 1300 m g for macroporous ordered silica. 

Covalent organic frameworks (COFs Sect. 3.1) 711-4,210 0.32-1.66" High thermeil stability porosity sensitive to air for B-conteiining COFs Highest MOP surface areas crystalline tunable pores [14, 20, 67]... 

Figure 1.9 ThevariationofH2adsorbed(wt%)atsaturationat77KwithBET (a)and Langmuir surface area (b) for porous MOFs, carbons, zeolites, silicas, polymers, and covalent organic frameworks (COFs). Reprinted with permission from K.M. Thomas, Dalton Trans., 9,1487-1505. Copyright (2009) Royal Society of Chemistry...

Nagai A, Guo Z, Feng X et al (2011) Pore surface engineering in covalent organic frameworks. Nat Commun 2 536... 

The presence of water vapour will define which materials can be used based on their hydrolytic stability. As an example metal-organic frameworks (MOFs) and covalent organic framework (COFs) are crystalline microporous materials which can exhibit exceptionally high surface areas and gas sorption capacities and, as such, have been proposed as potential materials for CCS. However, some of these materials can be unstable in the presence of moisture. The IRMOF series and the more recently produced COF materials are particularly unstable (e.g., loss of porosity at room temperature in air). Clearly, materials of this type would be unsuitable for CCS application. If such materials are to be used, more stable types are required for example, one class of MOF known as zeolitic imidazole frameworks (ZIFs) are reported to have greatly improved hydrolytic stability. 

A covalent organic hexameric framework containing stacked thieno[2,3- ]-thiophene-2,5-diyldiboronic acid, as the electron-donor, and polyol 2,3,6,7,10,11-hexahydroxytriphenylene, as a spacer, was shown to possess a high surface area as well as a 3 nm open pore size and stack in an AA arrangement, as confirmed by nitrogen sorption and powder X-ray diffraction (13ACIE2920). 

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