Guanidine-based Porous Materials For Carbon Dioxide Capture

Nowadays,the accumulation of atmospheric carbon dioxide has been widely blamed to pay most of the responsibility for global warming and climate change.Nitrogen-rich porous carbonous materials with esay desorption and excellent reproducibility reveal to be a class of emerging candidate for highly efficient and selective CO2 capture process.Therefore,the guanidine-type functional group was selected as the fundamental structure motif to construct guanidine-based nitrogen-rich porous polymeric materials by self-assembly of the corresponding precusors,aiming to explore the dependence between CO2 capture capacity and geometry.At the same time,the guanidine unit would endow its CO2 activation property to the fundamental sturcture of the above-mentioned porous material,which could potentially integrate both CO2 capture and its catalytic conversion in the present system.Such design was revealed by the following results:(1)The synthesis,characterization and absorption test of the guanidine-based porous polymeric materials.The reaction of benzene-1,4-diamine dihydrochloride,benzidine dihydrochloride,benzene-1,3,5-triamine trihydrochloride,N1,N1-bis(4-aminophenyl)benzene-1,4-diamine trihydrochloride,N1,N1-bis(4-aminophenyl)benzene-1,4-diamine trihydrochloride and 4,4',4'',4'''-(adamantane-1,3,5,7-tetrayl)tetraaniline tetrahydrochloride with the corresponding aromatic cyanamides afforded a series of guanidine-rich porous polymeric materials(CPAs).The average pore diameters of the as-prepared CPAs were in range of 2~4 nm due to the free rotation of the C-N single bond within the guanidine unit,and the highest BET specific surface area reached 118.32 m2/g at 273 K and 1 bar.The best CO2 capture capacity of the CPAs was around 7.05 wt%,and it could be retained to 5.88 wt% after 5 consecutive absorption-desorption runs.(2)The influence of structural geometry on CO2 capture capacity.The two kinds of CPA formed by the the reaction of benzene-1,4-diamine dihydrochloride with N,N',N''-(nitrilotris(benzene-4,1-diyl))tricyanamide and N1,N1-bis(4-aminophenyl)benzene-1,4-diamine trihydrochloride with N,N'-(1,4-phenylene)dicyanamide respectively had a similar average pore size and a approximately equal CO2 capture capacity(24 cm3/g).