skip to main content


Title: Molecularly engineering polymeric membranes for H2 / CO2 separation at 100–300 °C
Abstract

Over the last two decades, polymers with superior H2/CO2separation properties at 100–300 °C have gathered significant interest for H2purification and CO2capture. This timely review presents various strategies adopted to molecularly engineer polymers for this application. We first elucidate the Robeson's upper bound at elevated temperatures for H2/CO2separation and the advantages of high‐temperature operation (such as improved solubility selectivity and absence of CO2plasticization), compared with conventional membrane gas separations at ~35 °C. Second, we describe commercially relevant membranes for the separation and highlight materials with free volumes tuned to discriminate H2and CO2, including functional polymers (such as polybenzimidazole) and engineered polymers by cross‐linking, blending, thermal treatment, thermal rearrangement, and carbonization. Third, we succinctly discuss mixed matrix materials containing size‐sieving or H2‐sorptive nanofillers with attractive H2/CO2separation properties.

 
more » « less
Award ID(s):
1804996
NSF-PAR ID:
10453199
Author(s) / Creator(s):
 ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Journal of Polymer Science
Volume:
58
Issue:
18
ISSN:
2642-4150
Page Range / eLocation ID:
p. 2467-2481
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Although many porous materials, including metal–organic frameworks (MOFs), have been reported to selectively adsorb C2H2in C2H2/CO2separation processes, CO2‐selective sorbents are much less common. Here, we report the remarkable performance ofMFU‐4(Zn5Cl4(bbta)3, bbta=benzo‐1,2,4,5‐bistriazolate) toward inverse CO2/C2H2separation. The MOF facilitates kinetic separation of CO2from C2H2, enabling the generation of high purity C2H2(>98 %) with good productivity in dynamic breakthrough experiments. Adsorption kinetics measurements and computational studies show C2H2is excluded fromMFU‐4by narrow pore windows formed by Zn−Cl groups. Postsynthetic F/Clligand exchange was used to synthesize an analogue (MFU‐4‐F) with expanded pore apertures, resulting in equilibrium C2H2/CO2separation with reversed selectivity compared toMFU‐4.MFU‐4‐Falso exhibits a remarkably high C2H2adsorption capacity (6.7 mmol g−1), allowing fuel grade C2H2(98 % purity) to be harvested from C2H2/CO2mixtures by room temperature desorption.

     
    more » « less
  2. Abstract

    Although many porous materials, including metal–organic frameworks (MOFs), have been reported to selectively adsorb C2H2in C2H2/CO2separation processes, CO2‐selective sorbents are much less common. Here, we report the remarkable performance ofMFU‐4(Zn5Cl4(bbta)3, bbta=benzo‐1,2,4,5‐bistriazolate) toward inverse CO2/C2H2separation. The MOF facilitates kinetic separation of CO2from C2H2, enabling the generation of high purity C2H2(>98 %) with good productivity in dynamic breakthrough experiments. Adsorption kinetics measurements and computational studies show C2H2is excluded fromMFU‐4by narrow pore windows formed by Zn−Cl groups. Postsynthetic F/Clligand exchange was used to synthesize an analogue (MFU‐4‐F) with expanded pore apertures, resulting in equilibrium C2H2/CO2separation with reversed selectivity compared toMFU‐4.MFU‐4‐Falso exhibits a remarkably high C2H2adsorption capacity (6.7 mmol g−1), allowing fuel grade C2H2(98 % purity) to be harvested from C2H2/CO2mixtures by room temperature desorption.

     
    more » « less
  3. Abstract

    Porous materials with open metal sites have been investigated to separate various gas mixtures. However, open metal sites show the limitation in the separation of some challenging gas mixtures, such as C2H2/CO2. Herein, we propose a new type of ultra‐strong C2H2nano‐trap based on multiple binding interactions to efficiently capture C2H2molecules and separate C2H2/CO2mixture. The ultra‐strong acetylene nano‐trap shows a benchmarkQstof 79.1 kJ mol−1for C2H2, a record high pure C2H2uptake of 2.54 mmol g−1at 1×10−2 bar, and the highest C2H2/CO2selectivity (53.6), making it as a new benchmark material for the capture of C2H2and the separation of C2H2/CO2. The locations of C2H2molecules within the MOF‐based nanotrap have been visualized by the in situ single‐crystal X‐ray diffraction studies, which also identify the multiple binding sites accountable for the strong interactions with C2H2.

     
    more » « less
  4. Abstract

    Porous materials with open metal sites have been investigated to separate various gas mixtures. However, open metal sites show the limitation in the separation of some challenging gas mixtures, such as C2H2/CO2. Herein, we propose a new type of ultra‐strong C2H2nano‐trap based on multiple binding interactions to efficiently capture C2H2molecules and separate C2H2/CO2mixture. The ultra‐strong acetylene nano‐trap shows a benchmarkQstof 79.1 kJ mol−1for C2H2, a record high pure C2H2uptake of 2.54 mmol g−1at 1×10−2 bar, and the highest C2H2/CO2selectivity (53.6), making it as a new benchmark material for the capture of C2H2and the separation of C2H2/CO2. The locations of C2H2molecules within the MOF‐based nanotrap have been visualized by the in situ single‐crystal X‐ray diffraction studies, which also identify the multiple binding sites accountable for the strong interactions with C2H2.

     
    more » « less
  5. Abstract

    Metal–organic frameworks (MOFs) can efficiently purify hydrocarbons from CO2, but their rapid saturation, driven by preferential hydrocarbon adsorption, requires energy‐intensive adsorption–desorption processes. To address these challenges, an innovative approach is developed, enabling control over MOF flexibility through densification and defect engineering, resulting in an intriguing inverse CO2/C2 hydrocarbon selectivity. In this study, the densification process induces the shearing of the crystal lattice and contraction of pores in a defective CuBTC MOF. These changes have led to a remarkable transformation in selectivity, where the originally hydrocarbon‐selective CuBTC MOF becomes CO2‐selective. The selectivity values for densified CuBTC are significantly reversed when compared to its powder form, with notable improvements observed in CO2/C2H6(4416 vs 0.61), CO2/C2H4(15 vs 0.28), and CO2/C2H2(4 vs 0.2). The densified material shows impressive separation, regeneration, and recyclability during dynamic breakthrough experiments with complex quinary gas mixtures. Simulation studies indicate faster CO2passage through the tetragonal structure of densified CuBTC compared to C2H2. Experimental kinetic diffusion studies confirm accelerated CO2diffusion over hydrocarbons in the densified MOF, attributed to its small pore window and minimal interparticle voids. This research introduces a promising strategy for refining existing and future MOF materials, enhancing their separation performance.

     
    more » « less