Preparation of Unconventional Dendrimers that Contain Rigid NHTriazine Linkages and Peripheral tert‐Butyl Moieties for CO₂‐Selective Adsorption

Abstract

Three unconventional dendrimers that contained rigid NH-triazine linkages and peripheral tert-butyl moieties were prepared by using a convergent approach and characterized by (1)H and (13)C NMR spectroscopy, mass spectrometry, and elemental analysis. Based on a thermogravimetric analysis study, these dendrimers were observed to display thermal stability at about 300 °C. The NH-triazine moiety, which possessed protonated and proton-free nitrogen sites (like the imidazole unit), displayed the capture of polarizable CO2 molecules through hydrogen-bond and/or dipole-quadrupole interactions. In addition, the adsorption of various amounts of CO2 and N2 at different pressures suggests that the dendritic pores, which arise from the stacking of the middle co-planar and rim protuberant dendrimers, Gn -N∼N-Gn (n=1-3), either swell or shrink at high pressure, thus indicating that these dendrimers may have a breathing ability.

Design of a Peripheral Building Block for H-Bonded Dendritic Frameworks and Analysis of the Void Space in the Bulk Dendrimers

“…This study shows that triazine-based dendrimers have a potential application in separating N 2 from CO 2 in a N 2 - CO 2 mixture. However, we were not able to identify the mode of stacking of the dendritic molecules in the solid state in our previous work 63 . With bearing all this in mind, we employed piperazine and triazine as connecting units and 3,5-di- tert -butylamidobenzene as a peripheral moiety in this work to prepare small dendritic molecules.…”

“…A framework made of piperazine and triazine units with a BET area of ~165 m 2 /g was found to have the CO 2 sorption capacity as high as 5616 mg/g at 200 bar and 65 °C 65 . Previously, we reported that dendrimers containing triaminotriazine moiety show very different sorption behavior with respect to N 2 and CO 2 gases at high pressure; particularly, only CO 2 and almost no N 2 gas is adsorbed at 35 atm by the 3 rd generation dendrimers in the solid state 63 . This study shows that triazine-based dendrimers have a potential application in separating N 2 from CO 2 in a N 2 - CO 2 mixture.…”

Adsorbing Volatile Organic Chemicals by Soluble Triazine-Based Dendrimers under Ambient Conditions with the Adsorption Capacity of Pyridine up to 946.2 mg/g

“…On the other hand, dendrimers, generally with significant internal void spaces, are reported to adsorb metal ions or small molecules in solution for the purpose of catalyzing [ 26 , 27 ] and drug delivery [ 28 , 29 , 30 ]. As solids, dendrimers have also been demonstrated to contain dendritic void spaces and adsorb gases [ 31 , 32 ]. However, dendrimers have not yet been used as porous materials to adsorb VOCs.…”

Silica Functionalized by Bifunctional Dendrimers: Hybrid Nanomaterials for Trapping CO2

“…Different types of dendrimeric molecules have already been grafted on to silica, and a few examples of dendrimers used for trapping CO 2 have been recently presented: the use of poly(propyleneimine) (PPI) dendrimers included but not grafted on to silica for trapping CO 2 during the purification of gases and for CO 2 capture, and the use of polyol hyperbranched polymers in Mg/Al hydroxides for the reversible trapping of CO 2 . PAMAM dendrimers bound to organoclays, PPI dendrimers intercalated inside graphite oxide, triazine dendrimers alone or triazine dendrons grafted on to silica have also been proposed for trapping CO 2 .…”