Exceptional ammonia uptake by a covalent organic framework.
Covalent organic frameworks (COFs) are porous crystalline materials composed of light elements linked by strong covalent bonds. A number of these materials contain a high density of Lewis acid boron sites that can strongly interact with Lewis basic guests, which makes them ideal for the storage of corrosive chemicals such as ammonia. We found that a member of the covalent organic framework family, COF-10, shows the highest uptake capacity (15 mol kg⁻¹, 298 K, 1 bar) of any porous material, including microporous 13X zeolite (9 mol kg⁻¹), Amberlyst 15 (11 mol kg⁻¹) and mesoporous silica, MCM-41 (7.9 mol kg⁻¹). Notably, ammonia can be removed from the pores of COF-10 by heating samples at 200°C under vacuum. In addition, repeated adsorption of ammonia into COF-10 causes a shift in the interlayer packing, which reduces its apparent surface area to nitrogen. However, owing to the strong Lewis acid-base interactions, the total uptake capacity of ammonia and the structural integrity of the COF are maintained after several cycles of adsorption/desorption.
Center for Reticular Chemistry at the California NanoSystems Institute, Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California 90095, USA.
Christian J
CJ
Doonan
David J
DJ
Tranchemontagne
T Grant
TG
Glover
Joseph R
JR
Hunt
Omar M
OM
Yaghi
D000327:Adsorption; D000641:Ammonia / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry*; D016062:Porosity
D009930:Organic Chemicals; D000641:Ammonia