Robust tri(4-ethynylphenyl)amine-based porous aromatic frameworks for carbon dioxide capture

Abstract

We report here the synthesis and carbon dioxide capture of a series of porous aromatic framework (PAF) materials assembled using tri(4-ethynylphenyl)amine and various aryl halides via Sonogashira-Hagihara coupling reactions. These PAF materials show moderate surface areas ranging from 370 m 2 g À1 to 953 m 2 g À1 . The functional groups, such as -COOH, -NH 2 and -OH, are incorporated into the backbone of the PAF materials. The isosteric heats of CO 2 and CO 2 /N 2 selectivities for these PAFs are calculated based on the CO 2 and N 2 adsorption isotherms measured at 273 and 298 K. It is found that the -NH 2 functionalized network shows the highest isosteric heat of CO 2 and CO 2 /N 2 selectivity. In addition, the -COOH functionalized network displays the highest CO 2 uptake in terms of per unit areas (4.37 mmol m À2 , 273 K). The results indicate the incorporation of functional groups is effective for synthesizing CO 2philic PAF networks with enhanced interaction with CO 2 molecules.

Bifunctionalized conjugated microporous polymers for carbon dioxide capture

“…Hysteresis loop upon desorption was observed persisting to the relative pressures of 0.5 for the polymer networks, which is consistent with elastic deformations or swelling as a result of gas sorption [40]. The apparent Brunauer-Emmet-Teller (BET) surface areas were found to be 1316 and 1470 m 2 g À1 for BFCMP-1 and BFCMP-2, respectively, which are comparable to those of many reported CMPs [8,41,42], and much higher than those of the functionalized CMPs [17,27,29,43]. Compared with BFCMP-1, BFCMP-2 showed a little higher surface area, which could be attributed to the higher crosslinked polymer structure of BFCMP-2 from the linker of 1,3,5-trietnylbenze with more connectivities than 1,4-dietnylbenze.…”

“…Both of the bifunctionalized polymer networks showed very similar adsorption selectivities of 4.0 for CO 2 /CH 4 and 30 for CO 2 /N 2 at 273 K. The CO 2 / N 2 adsorption selectivity by both of the polymer networks is comparable to that of some other MOPs under the similar conditions, such as the triazine-functionalized CMPs (9.0e25.2 at 298 K) [50], the amide-functionalized CMPs (8.5e12 at 298 K) [26], the imine-linked porous polymer frameworks (14.5e20.4 at 273 K) [52], the carbazolic porous organic frameworks (19À37 at 273 K) [58], and the nanoporous azo-linked polymers (30e43 at 273 K) [34], though it is lower than that of some other reported MOPs with the CO 2 /N 2 adsorption selectivity higher than 100, such as the azobridged covalent organic polymer of Azo-COP-2 with a CO 2 /N 2 adsorption selectivity of 109 at 273 K [59], the porous benzimidazole-linked polymer of BILP-2 with a CO 2 /N 2 adsorption selectivity of 113 at 273 K [48], the PPN-6-SO 3 NH 4 with a CO 2 /N 2 adsorption selectivity of 196 at 295 K, and the tri(4-ethynylphenyl) amine-based porous aromatic framework with amine groups of PAF-33eNH 2 with the CO 2 /N 2 adsorption selectivity as high as 250 at 273 K [29]. However, the absolute amount of CO 2 adsorbed was only 1.19 mmol g À1 for PAF-33eNH 2 at 273 K/1.0 bar [29], much lower than that of the BFCMP-2 (2.77 mmol g À1 at 273 K/1.13 bar) in this work. Ideally, high uptake and selectivity are both required for practical applications.…”

“…The CO 2 uptake capacity of BFCMP-2 is higher than that of many reported non-functionalized and functionalized CMPs produced by Sonogashira-Hagihara coupling reaction at the same conditions, such as the pyrene-based porous aromatic frameworks (0.90e1.15 mmol g À1 ) [49], the hexabenzocoronenebased porous organic polymers (e.g. 2.05 mmol g À1 for HBC-POP-1) [30], the tri(4-ethynylphenyl)amine-based porous aromatic frameworks (1.19e2.50 mmol g À1 ) [29], the CMPs functionalized with carboxylic acids, amines, hydroxyl groups, and methyl groups, respectively (e.g. 1.80 mmol g À1 for CMP-1-(OH) 2 ) [17], the triazinefunctionalized CMPs (e.g.…”

“…Although the introduction of polar functional groups by post modification leads to the enhancement of binding affinity between the adsorbent and CO 2 molecules, the surface area of the modified MOPs is much lower than that of the parent materials because the functional groups introduced will occupy some pores [24,26e28], which makes the decrease of CO 2 -sorption capacity instead in some cases [17,26,29]. It has been proved that palladium-catalyzed SonogashiraeHagihara cross-coupling polymerization is an efficient method to produce highly porous CMPs and functionalized CMPs with enhanced CO 2 -sorption capacity.…”

Targeted synthesis of porous aromatic frameworks with stimuli-responsive adsorption properties

“…(4) The characteristic N=N stretching band at around 1480 cm −1 is present in the spectrum of the final product. These observations indicate that the PAF materials have the desired skeletons [24]. 13 C solid-state NMR cross-polarization (CP)/MAS spectroscopy is a powerful tool for probing the local structures of polymers.…”