Ultrathin membrane with robust and superior CO2 permeance by precision control of multilayer structures

https://doi.org/10.1016/j.cej.2023.142087Get rights and content

Highlights

  • A simple spin coating technique was used to create a high-performance membrane.

  • Controlling the chemistry of the gutter layer formation used for the first time.

  • This novel method enabled controlling the precise thickness of the gutter layer.

  • The membranes showed superior CO2 permeances of >17,000 GPU.

  • This robust technique showed a 98.4% success rate in producing membranes.

Abstract

Reducing CO2 emissions in the atmosphere is an urgent task to resolve serious environmental issues including global warming. Polymer-based ultrathin film composite (UTFC) membranes are an attractive strategy compared with other CO2 separation technologies due to their lower environmental impacts, higher cost-efficiency, and ease of scale-up. However, improving the gas separation performance with a simplified fabrication process is still needed for practical uses. The key to designing a high-performing gas separation composite membrane is the development of a highly gas-permeable gutter layer and ultrathin high-selective top layer. While the top layers in nanoscale thicknesses have been recently developed, achieving high gas permeance is still challenging due to the existing less controlled gutter layer. Gutter layers afford a uniform and highly permeable base to which an ultrathin selective layer can be coated, minimising the gas permeance loss while maintaining the gas selectivity. Polydimethylsiloxane (PDMS) is a common and widely used material for gutter layers due to its inherent high gas permeability. However, the CO2 permeance of these films is limited to between 1,500 and 5,000 GPU as the current uncontrollable fabrication methods tend to produce thicker layers. Here we report a new fabrication method with precise thickness control, which results in ultrathin gutter layers showing consistent CO2 permeance with 13,920 ± 1,770 GPU without any reduction in CO2/N2 selectivity. When this gutter layer was coated with a selective layer of PolyActive™ (PA), the resultant PAN/PDMS/PA composite membranes outperformed previously reported UTFC membranes with a CO2 permeance of 3,555 GPU and CO2/N2 selectivity of 40.

Introduction

Membrane separation has been acknowledged as a proven technology over the other separation techniques due to its energy efficiency and cost-effectiveness in broad applications, such as ammonia production [1], wastewater treatment [2], solar cells [3], and desalination using electrodialysis and reverse osmosis [4], [5]. Gas separation membranes, in particular, have the potential to selectively separate CO2 gas molecules from mixed gas steams including emissions from fossil fuel-based power stations, cement manufacture and in the future direct capture from the atmosphere [6]. The main mechanisms for membrane gas separation include solution-diffusion and molecular sieving. It is considered the most promising method due to its simple separation with high processability, low energy consumption, and low capital costs [7], [8]. Gas separation membranes are generally prepared as either dense polymeric membranes or ultrathin film composite (UTFC) membranes. Dense polymeric membranes can offer a relatively high selectivity of gas pairs; however, their gas permeabilities are quite poor since this is an inherent measure of the material’s performance and not dependent on the thickness [9], [10]. Instead, UTFC membranes can result in higher gas permeance by reducing their thickness as described by Winston Ho and Kamalesh K. Sirkar [11]. In recent years, the absolute gas permeance of a membrane has been recognized as more important than its gas permeability, as it is a true measure of the throughput a membrane can achieve. Therefore, the development and design of UTFC membranes are crucial for high-performance membranes. UTFC membranes typically consist of multiple layers including a gas selective layer, an intermediate gutter layer, and a highly porous supportive layer [12], [13], [14]. The majority of recent approaches have been successful at improving the selective layer. Although there are recent attempts in improving the gutter layer, it often involves additional approaches or extra additives [15]. The important role of the gutter layer is to offer a flat uniform surface able to accommodate an ultrathin selective layer, overcoming the uneven surfaces of the porous substrate that causes a reduction in gas permeance [16]. However, the gutter layer often is much thicker than the desired target, due to the partial filling of the pores in the supporting layer. Numerous approaches have been explored to improve the gutter layer performance, including investigating different materials [17], incorporating additives [15], [18] and trialling casting techniques such as chemical vapour deposition [19], [20], sputtering [21], dip-coating [22] and spin-coating [23], [24]. All these approaches have been either provided less than ideal performance or involve overly complicated procedures.

Polydimethylsiloxane (PDMS) is commonly used in gutter layer design, due to its high CO2 permeability along with great processability [16]. Yoo et al. used a series resistance model of the CO2 permeability of PDMS dense membranes to simulate the CO2 permeance of PAN/PDMS membranes relative to their thicknesses [25]. According to their modelling, CO2 permeances of up to 14,000 GPU could be achieved for a 200 nm PDMS layer, with thinner layers predicted to offer even higher CO2 permeances [25]. Despite this predicted performance, previous reported laboratory-scale experiments have only achieved PDMS gutter layer CO2 permeances up to 5,000 GPU due to the previously described challenges caused during the fabrication process such as the formation of pin holes and the materials filling the pores of the membrane support [14], [26], [27], [28]. Although we have recently reported a PDMS membrane embedded with metal–organic framework (MOF) nanosheets showing CO2 permeance of 10,450 GPU, currently there is no simple procedure that can produce pure PDMS gutter layers with CO2 permeances of >5,000 GPU [15].

In this study, we report a newly developed method for producing a PDMS gutter layer using a conventional membrane fabrication approach but with precise thickness control by using the chemistry of pre-crosslinking. With this simple and new approach, we can consistently produce super-permeable ultrathin pristine PDMS layers with extremely high CO2 permeance around 15,000 GPU (repeatability of 98.4 %) with the highest value reaching 17,064 GPU. We investigated the crucial factors in the process for achieving such membranes. Using this ultra-permeable gutter layer, we also fabricated a UTFC membrane consisting of a top PolyActive™ (PA) selective layer and achieved superior gas separation performance of the UTFC membrane.

Section snippets

Materials

Aminopropyl-terminated polydimethylsiloxane (Mn 5.0 kDa; PDMS-bis-NH2) was purchased from Gelest and used as received. The crosslinker, 1,3,5-benzenetricarbonyl trichloride (TMC, 98 %, Sigma-Aldrich), was stored and used in an inert N2 atmosphere to avoid hydrolysis of acyl chlorides with atmospheric moisture. Chloroform (AR grade, >99 %) and n-hexane (AR grade, >99 %) were purchased from Chem-Supply. Deuterated chloroform (CDCl3, >99.8 %, Cambridge Isotope Laboratories) was used for 1H NMR

Properties influencing PDMS gutter layer formation

In the conventional preparation of PDMS gutter layers, PDMS macromonomer is mixed with a crosslinker in solution prior to spin coating. Sufficient time in solution is required to ensure a high degree of crosslinking in solution before casting onto a substrate because the high content of flexible siloxane linkages in the PDMS backbone can enhance gas permeability since gases are transported via a solution-diffusion mechanism [22]. Previous publications have reported the thicknesses of these PDMS

Conclusion

A superior method for forming ultrathin crosslinked PDMS gutter layers on a substrate was investigated by control and optimization of the pre-crosslinking time in a solution state. This is the first time the pre-crosslinking time was precisely controlled for membrane formation that resulted in superior gas separation performance. Defect-free ultrathin PAN/PDMS membranes were successfully prepared with excellent CO2 permeation properties within 220 s to 580 s of pre-crosslinking time. The

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

We thank Billy Murdoch at RMIT University’s Microscopy and Microanalysis Facility (RMMF) for the XPS measurement.

References (83)

  • H. Nagasawa et al.

    Atmospheric-pressure plasma-enhanced chemical vapor deposition of microporous silica membranes for gas separation

    J Memb Sci.

    (2017)
  • H.T. Hoang et al.

    Fabrication and characterization of dual sputtered Pd–Cu alloy films for hydrogen separation membranes

    Materials Letters

    (2004)
  • M.J. Yoo et al.

    Ultrathin gutter layer for high-performance thin-film composite membranes for CO2 separation

    J Memb Sci.

    (2018)
  • G. Firpo et al.

    Permeability thickness dependence of polydimethylsiloxane (PDMS) membranes

    J Memb Sci.

    (2015)
  • D. Zhao et al.

    Improved CO2 separation performance of composite membrane with the aids of low-temperature plasma treatment

    J Memb Sci.

    (2019)
  • J.M.P. Scofield et al.

    Development of novel fluorinated additives for high performance CO2 separation thin-film composite membranes

    J Memb Sci.

    (2016)
  • R. Dahiya et al.

    PDMS residues-free micro/macrostructures on flexible substrates

    Microelectron Eng.

    (2015)
  • L. Zhao et al.

    Comparative investigation of polymer membranes for post-combustion capture

    Energy Procedia.

    (2013)
  • T.C. Merkel et al.

    Power plant post-combustion carbon dioxide capture: An opportunity for membranes

    J Memb Sci.

    (2010)
  • C.Z. Liang et al.

    High-performance multiple-layer PIM composite hollow fiber membranes for gas separation

    J Memb Sci.

    (2018)
  • R.S. Bhavsar et al.

    Ultrahigh-permeance PIM-1 based thin film nanocomposite membranes on PAN supports for CO2 separation

    J Memb Sci.

    (2018)
  • M. Liu et al.

    High-throughput CO2 capture using PIM-1@MOF based thin film composite membranes

    Chemical Engineering Journal.

    (2020)
  • K. Xie et al.

    Increasing both selectivity and permeability of mixed-matrix membranes: Sealing the external surface of porous MOF nanoparticles

    J Memb Sci.

    (2017)
  • C.-Y. Tsai et al.

    Dual-layer asymmetric microporous silica membranes

    Journal of Membrane Science

    (2000)
  • L.S. White et al.

    Extended field trials of Polaris sweep modules for carbon capture

    J Memb Sci.

    (2017)
  • L. Ye et al.

    Sustainable ammonia production enabled by membrane reactor

    Nat Sustain.

    (2022)
  • J. Nambi Krishnan et al.

    Review of Thin Film Nanocomposite Membranes and Their Applications in Desalination

    Front Chem

    (2022)
  • R. R. Zolandz and G. K. Fleming, in Membrane Handbook, W. S. W. Ho and K. K. Sirkar, eds, Van Nostrand Reinhold...
  • M. Liu et al.

    Two-dimensional nanosheet-based gas separation membranes

    J Mater Chem A Mater.

    (2018)
  • J.M.P. Scofield et al.

    High-performance thin film composite membranes with well-defined poly(dimethylsiloxane) -b-poly(ethylene glycol) copolymer additives for CO2 separation

    Journal of Polymer Science Part A: Polymer Chemistry

    (2015)
  • J.M.P. Scofield et al.

    Blends of fluorinated additives with highly selective thin-film composite membranes to increase CO2 permeability for CO2/N2 Gas Separation applications

    Ind. Eng. Chem. Res.

    (2016)
  • M. Liu et al.

    Ultrapermeable composite membranes enhanced via doping with amorphous MOF nanosheets

    ACS Cent Sci.

    (2021)
  • M. Liu et al.

    Postcombustion carbon capture using thin-film composite membranes

    Acc Chem Res.

    (2019)
  • N.D. Boscher et al.

    Metal – organic covalent network chemical vapor deposition for gas separation

    Adv. Mater.

    (2016)
  • S.S. Madaeni et al.

    Effect of coating method on gas separation by PDMS / PES Membrane

    Polymer Engineering & Science

    (2013)
  • C. Chi et al.

    Facile preparation of graphene oxide membranes for gas separation

    Chem. Mater.

    (2016)
  • K. Norrman et al.

    Studies of spin-coated polymer films

    Annual Reports on the Progress of Chemistry - Section C.

    (2005)
  • P. Li et al.

    High-performance multilayer composite membranes with mussel-inspired polydopamine as a versatile molecular bridge for CO2 Separation

    ACS Appl Mater Interfaces.

    (2015)
  • C.Z. Liang et al.

    Ultrahigh flux composite hollow fiber membrane via highly crosslinked PDMS for Recovery of hydrocarbons: propane and propene

    Macromol. Rapid Commun.

    (2018)
  • R. Selyanchyn et al.

    Thickness effect on CO2/N2 separation in double layer Pebax-1657®/PDMS membranes

    Membranes (Basel).

    (2018)
  • Q. Fu et al.

    Highly permeable membrane materials for CO2 capture

    J Mater Chem A Mater.

    (2013)
  • Cited by (14)

    View all citing articles on Scopus
    View full text