Pseudopeptide bioconjugate additives for CO₂ separation membranes

Abstract

1:1[ / -N -Bn-hydrazino] pseudopeptide−polymer bioconjugates were synthesized and investigated as additives in a reference gas separation membrane (Pebax ® ) for CO 2 capture. Pebax ® is a polyether block amide thermoplastic elastomer provided by Arkema and is already well known for its good performance for CO 2 separations. First, dimer and tetramer pseudopeptides were synthesized and their terminal amine was modified into a 'clickable' alkyne group in view of coupling. Second, an -azido acrylic poly(ethylene glycol)-based oligomer was obtained by single-electron transfer living radical polymerization and the two partners were coupled using copper(I) catalyzed alkyne-azide cycloaddition (CuAAC) 'click' chemistry. The pseudopeptides and their bioconjugates were then assessed as original additives in Pebax ® membranes for CO 2 /CH 4 and CO 2 /N 2 separations. The permeation data were analyzed according to the solution-diffusion model. Compared to pseudopeptides, the pseudopeptide−polymer bioconjugates enabled the membrane properties to be greatly improved with better permeability (×1.5) and a good constant selectivity for CO 2 capture. The best membrane properties were obtained with 3 eq. wt% of the tetramer-based bioconjugate with a CO 2 permeability of 194 Barrer (+46% compared to that of Pebax ® ) and constant selectivity ( CO 2 /N 2 = 44 and CO 2 /CH 4 = 13).

A lysine-based 2:1-[α/aza]-pseudopeptide series used as additives in polymeric membranes for CO2 capture: synthesis, structural studies, and application

“…The best CO 2 permeability (148 Barrer) and ideal selectivity (47.6) obtained in this work with the new deprotected dimer additive are very close to those reported in our first work on other pseudopeptide bio-inspired additives in Pebax 1074 membranes for CO 2 separation in the same operating conditions (pressure: 2 bar, temperature: 35 °C). 55 Furthermore, in the former work, a dimer pseudopeptide was also better performing than the corresponding tetramer, due its lower structuration.…”

“…In 2016, we have reported the first work on pseudopeptide additives and their corresponding bioconjugates with a CO 2 -philic polymeric part for greatly improving CO 2 permeability through CO 2 separation membranes. 55 In 2019, Prasad et al have used sericin polypeptide ( i.e. a waste product of the silk industry) as additive in chitosan membranes for CO 2 separations.…”

“…In the future, more molecular dynamics simulations in explicit membrane environment would be an interesting to investigate in order to decipher more precisely the peptide structure/membrane properties. Additionally, following our related work on the first bio-inspired pseudopeptide additives for CO 2 separation membranes, 55 the new deprotected dimer could be used for developing new bioconjugates based on CO 2 -philic oligomers for further improving membrane properties for CO 2 separations including CO 2 post-combustion capture for preventing the associated global climatic changes.…”

“…The gas permeation properties were determined by the “time-lag” method using an experimental procedure described in our former work on other bio-based pseudopeptide for CO 2 capture membranes. 55 The gas permeation properties were determined for CO 2 and N 2 pure gases (high purity gases purchased from Messer Company) at 35 °C and 2 bar. The gas permeation experiments were repeated five times for each membrane and each tested gas to assess the reproducibility from the corresponding experimental errors.…”

“…In this work, seven aza-pseudopeptide oligomers (6b, 6b ′ , 7a, 7c, 7c ′ , 8c, and 8c ′ ) from the synthesized 2:1-[a/aza]-series (Table 2) were tested as additives in Pebax® 1074 membrane, already known for its good performance for CO 2 capture 55,75,76 (ESI, Fig. S14 †).…”