Enhancement of CO2/CH4 separation performances of 6FDA-based co-polyimides mixed matrix membranes embedded with UiO-66 nanoparticles
Graphical abstract
Introduction
The number of investigations on metal-organic frameworks (MOFs) has grown rapidly in the past few years due to their promising applications in gas storage and separation. The potential application varies from the eminent purpose of natural gas sweetening and CO2 post-combustion capture to the in-house air purification. MOFs can be classified by their three-dimensional crystalline frameworks with permanent porosity, formed with metal-based clusters linked by organic ligands [1]. The infinite possibilities of metal and linker selections in the synthesis of MOFs give researchers a variety of coordination geometry choices, i.e., tetrahedral, pyramidal or bi-pyramidal, trigonal or octahedron [2]. This design flexibility allows the MOFs to be attuned to their intended purposes. Additionally, their inherent properties are remarkable advantages, such as high CO2 uptakes (e.g. HKUST-1 of 7.32 [3] and 10.71 mmol·g−1 [4], MIL-53 of 10.02 mmol·g−1 [4], MIL-100 of 9.98 mmol·g−1 [5], MIL-101 of 7.20 mmol·g−1 [6]), open porous framework structures with large accessible pore volumes, tuneable pore affinity and most importantly their relatively high chemical and thermal stabilities. Several intensive reviews on MOFs for CO2 separation [7], [8], [9], [10] have been made available, and several others [1], [2], [11] comprehensively discussed on the MOF synthesis. The incorporation of these MOFs dispersed into the polymer continuous-phase as mixed matrix membranes (MMMs) has been reported using both low flux (e.g., PSF [12], PVAc [13] and PBI [14]) and high flux (e.g., rubbery PDMS [15] and glassy 6FDA-DAM [16], [17]) polymers.
Scientific attention towards the relatively new class of highly crystalline zirconium-based MOFs, especially UiO-66 (UiO: University of Oslo) grows rapidly. UiO-66 is based on a Zr6O4(OH)4 octahedron, forming 12-fold lattices connected by the organic linker, 1,4-benzene-dicarboxylate (BDC) (Fig. 1a) [18]. This zirconium terephthalate has high surface area, of experimental values 850–1300 m2·g−1 [12], [19], [20], [21], and the theoretically accessible surface of 1021 m2·g−1 [22]. The microporous framework composes of centric octahedral cages (ca. 11 Å) each connect with eight corner tetrahedral cages (ca. 8 Å) by means of trigonal windows (ca. 6 Å). The crystal face-centered-cubic contributes to its high stability towards heat (reported between 430 and 540 °C [23], [24]), pressure [25], water [25], [26], common solvents [25], even strong acid (HCl) and base (NaOH) [24]. The UiO-66 also possesses low heat adsorption with the increase of CO2 and CH4 loading, due to its bulky and non-polar aromatic ring which sterically hinders the highly adsorptive metal cluster to adsorb the heat [22], [27]. This is another added-value feature which is very desirable for thermal stability and lower cost regeneration.
Khdhayyer et al. [28] have recently published their findings regarding the incorporation of UiO-66 into the highly permeable polymer of intrinsic microporosity (PIM-1). The CO2 permeability was increased to 7610 Barrer, obtaining a 60% improvement with 23 wt% of UiO-66 loading. The CO2/CH4 selectivity, however, decreased with loading more than 9 wt%. Castarlenas et al. [12] reported H2/CH4 and CO2/CH4 separation with UiO-66 MMMs, where the H2/CH4 selectivity improved by 6.5% in polysulfone Udel® 3500-P and 7.7% in polyimide Matrimid® with 32 wt% loading. Remarkable H2 permeability improvements of 475% and 148% were recorded for the stated MMMs, respectively. They also reported a 3-fold CO2 permeability enhancement in the CO2/CH4 mixed gas separation, while the selectivity increased by 21% and 31%, respectively for Udel® 3500-P (32 wt% UiO-66) and Matrimid® (16 wt% UiO-66). Nik et al. [19] optimized 6FDA-ODA gas separation performance by incorporating 25 wt% of the MOF. They improved the CO2 permeability by 3.5 folds while maintaining the CO2/CH4 selectivity. Anjum et al. [21] also obtained an enhancement in membrane CO2/CH4 separation performance when embedding 30 wt% UiO-66 in polyimide Matrimid®. Shen et al. [29] utilized polyether block amide (PEBAX MH 1657) for their CO2/N2 binary gas MMM and achieved the best selectivity with 7.5 wt% UiO-66 loading. The selectivity and CO2 permeability were improved by 31% and 73%, respectively. Higher loading addition, unfortunately, decreased the CO2/N2 selectivity, even to a lower performance than that of the base polymer. Several publications have been made on UiO-66 MMMs for different applications, such as pervaporation [26], nanofiltration [30] and reverse osmosis [31].
We aimed to enhance CO2/CH4 gas separation of low and high fluxes 6FDA-polyimides, by making MMMs with different loadings of MOF UiO-66 nanoparticles. The nanoparticles, 50, 100 and 200 nm in size, were incorporated into three types of 6FDA based copolyimides with different aromatic diamine moieties, namely 6FDA-BisP, 6FDA-ODA and 6FDA-DAM. The chemical structures of the glassy polyimides are presented in Fig. 1b–d.
Section snippets
UiO-66 syntheses
The synthesis of the UiO-66 nanoparticles (ca. 50 nm in size) was conducted accordingly to the literature [32], at 1–1 M ratio of zirconium (IV) chloride (ZrCl4, ≥99.5% trace metal basis, Sigma-Aldrich) to benzene-1,4-dicarboxylic acid (BDC, 98%, Sigma-Aldrich) in N,N-dimethylformamide (DMF, ≥99.9%, Sigma-Aldrich) with a small addition of water. Commonly, 1.71 mmol (0.40 g) of ZrCl4 was dissolved in 100 mL of DMF at room temperature by sonication, before the addition of equimolar BDC (0.28 g)
Filler characterization
UiO-66 nanoparticles with size ca. 50 nm and BET surface area of 951 ± 14 m2·g−1, close to the accessible theoretical surface of 1021 m2·g−1 [22], were synthesized. Fig. 2a (inserted) shows the XRD pattern of the UiO-66 in good agreement with the literature [24]. Fig. 2a corresponds to the TGA characterization, where the negligible weight loss below 100 °C is suggested to be an initial solvent loss, while the latter drop until 300 °C is attributed to the dehydration of the Zr6O4(OH)4 nodes to Zr
Conclusion
We report the successful synthesis of high surface area Zr-based MOF UiO-66, with a uniform nanoparticle size of ca. 50 nm, appropriate crystallinity, and excellent thermal stability, as well as the fabrication of UiO-66 mixed matrix membranes with three 6FDA-based co-polyimides. Upon obtaining excellent MOF-polymer interaction with ca. 50 nm UiO-66 (and less agglomeration than using 100 and 200 nm particles), the presence of the MOF contributed to the increase of the membrane free volumes. The
Acknowledgements
The authors acknowledge the financial support of EACEA/European Commission, within the “Erasmus Mundus Doctorate in Membrane Engineering – EUDIME” (ERASMUS MUNDUS Programme 2009-2013, FPA n. 2011-0014, SGA n. 2012-1719), Operational Programme Prague – Competitiveness (CZ.2.16/3.1.00/24501), “National Program of Sustainability“ of Czech Republic, (NPU I LO1613) MSMT-43760/2015 and (MAT2016-77290-R) from the Spanish MINECO and FEDER, the Aragón Government (DGA, T05) and the European Social Fund.
References: (73)
- et al.
Extremely enhanced CO2 uptake by HKUST-1 metal-organic framework via a simple chemical treatment
Micropor. Mesopor. Mater.
(2014) - et al.
A comparative investigation of CO2 adsorption on powder and pellet forms of MIL-101
J. Taiwan Inst. Chem. Eng.
(2017) - et al.
Opportunities and challenges of MOF-based membranes in gas separations
Sep. Purif. Technol.
(2015) - et al.
Metal organic framework membranes for carbon dioxide separation
Chem. Eng. Sci.
(2015) - et al.
Metal organic framework based mixed matrix membranes: an increasingly important field of research with a large application potential
Micropor. Mesopor. Mater.
(2013) - et al.
Gas separation with mixed matrix membranes obtained from MOF UiO-66-graphite oxide hybrids
J. Membr. Sci.
(2017) - et al.
Polyvinyl acetate/titanium dioxide nanocomposite membranes for gas separation
J. Membr. Sci.
(2013) - et al.
High performance ZIF-8/PBI nano-composite membranes for high temperature hydrogen separation consisting of carbon monoxide and water vapor
Int. J. Hydrogen Energy
(2013) - et al.
Free-standing ZIF-71/PDMS nanocomposite membranes for the recovery of ethanol and 1-butanol from water through pervaporation
J. Membr. Sci.
(2017) - et al.
High performance ZIF-8/6FDA-DAM mixed matrix membrane for propylene/propane separations
J. Membr. Sci.
(2012)
Relationship between mixed and pure gas self-diffusion for ethane and ethene in ZIF-8/6FDA-DAM mixed-matrix membrane by pulsed field gradient NMR
J. Membr. Sci.
Functionalized metal organic framework-polyimide mixed matrix membranes for CO2/CH4 separation
J. Membr. Sci.
High-performance UiO-66/polyimide mixed matrix membranes for ethanol, isopropanol and n-butanol dehydration via pervaporation
J. Membr. Sci.
Mixed matrix membranes based on UiO-66 MOFs in the polymer of intrinsic microporosity PIM-1
Sep. Purif. Technol.
UiO-66-polyether block amide mixed matrix membranes for CO2 separation
J. Membr. Sci.
Fabrication of new composite membrane filled with UiO-66 nanoparticles and its application to nanofiltration
Sep. Purif. Technol.
Polymer brushes on metal-organic frameworks by UV-induced photopolymerization
Polym. Chem.
Preparation and enhanced CO2 adsorption capacity of UiO-66/graphene oxide composites
J. Ind. Eng. Chem.
Amine-functionalized zeolite FAU/EMT-polyimide mixed matrix membranes for CO2/CH4 separation
J. Membr. Sci.
Synthetic 6FDA-ODA copolyimide membranes for gas separation and pervaporation: functional groups and separation properties
Polymer (Guildf.)
Highly permeable zeolitic imidazolate framework (ZIF)-71 nano-particles enhanced polyimide membranes for gas separation
J. Membr. Sci.
A critical review of free volume and occupied volume calculation methods
J. Membr. Sci.
Correlation and prediction of gas permeability in glassy polymer membrane materials via a modified free volume based group contribution method
J. Membr. Sci.
ZIF-8 continuous membrane on porous polysulfone for hydrogen separation
J. Membr. Sci.
The strategies of molecular architecture and modification of polyimide-based membranes for CO2 removal from natural gas-a review
Prog. Polym. Sci.
Investigation of CO2-induced plasticization in fluorinated polyimide membranes via molecular simulation
J. Membr. Sci.
Formation of defect-free 6FDA-DAM asymmetric hollow fiber membranes for gas separations
J. Membr. Sci.
Mixed-matrix membranes incorporated with porous shape-persistent organic cages for gas separation
J. Colloid Interface Sci.
Study of different titanosilicate (TS-1 and ETS-10) as fillers for mixed matrix membranes for CO2/CH4 gas separation applications
J. Membr. Sci.
Gas separation performance of 6FDA-DAM-ZIF-11 mixed-matrix membranes for H2/CH4 and CO2/CH4 separation
Sep. Purif. Technol.
Molecular sieving realized with ZIF-8/Matrimid?? mixed-matrix membranes
J. Membr. Sci.
Gas transport properties in thermally cured aromatic polyimide membranes
J. Membr. Sci.
Decarboxylation crosslinking of polyimides with high CO2/CH4 separation performance and plasticization resistance
J. Membr. Sci.
Natural gas purification and olefin/paraffin separation using thermal cross-linkable co-polyimide/ZIF-8 mixed matrix membranes
J. Membr. Sci.
Effects of CO2 exposure and physical aging on the gas permeability of thin 6FDA-based polyimide membranes. Part 1. Without crosslinking
J. Membr. Sci.
Analysis of permeation transients of pure gases through dense polymeric membranes measured by a new permeation apparatus
J. Membr. Sci.
Cited by (66)
UiO-66-based metal-organic frameworks for CO<inf>2</inf> catalytic conversion, adsorption and separation
2024, Separation and Purification TechnologyMixed matrix membranes comprising 6FDA-based polyimide blends and UiO-66 with co-continuous structures for gas separations
2023, Separation and Purification TechnologyCO<inf>2</inf>separation of fluorinated 6FDA-based polyimides, performance-improved ZIF-incorporated mixed matrix membranes and gas permeability model evaluations
2022, Journal of Environmental Chemical EngineeringCitation Excerpt :In our opinion, the particle size range is highly suitable for incorporation into the polymer as MMM. The smaller nanoparticles (e.g., 40–60 nm ZIF-8 and ∼50 UiO-66 in 6FDA-polyimides [13,14]) are prone to a higher degree of aggregation. In the presence of big agglomeration, purportedly, the polymer matrix will be unable to surround the agglomerates, leading to void formation and resulting in non-selective gas diffusion [13,38].
Sulfonated TiO<inf>2</inf> quantum dots enabled constructing of bicarbonate highways in quaternary ammonium poly (ether ether ketone) membranes for efficient CO<inf>2</inf> separation
2022, Journal of Membrane ScienceCitation Excerpt :Although these polymers show relatively low gas separation performance, they have become “benchmarks” to evaluate the new filler materials. In recent years, a variety of new polymers (e.g. polyimide [12], inherent porous polymers [13], etc.) have been employed as polymer matrix in the preparation of MMMs for gas separation by virtue of flexible molecular structure design, distinctive microphase separation structure, or intrinsic microporosity. These polymers show much better gas permeability and fairly good CO2/gas selectivity.
Enhanced CO<inf>2</inf>-capture performance of polyimide-based mixed matrix membranes by incorporating ZnO@MOF nanocomposites
2022, Separation and Purification TechnologyCitation Excerpt :Among the reported fillers, MOFs are promising fillers for gas separation because of their high porosity and good thermal stability [17,18]. For example, Ahmad et al. [19] incorporated UiO-66 into polyimide to increase the CO2 permeability by 92% without sacrificing the CO2/CH4 selectivity. To further improve the dispersion of MOFs in polymer matrix and enhance the affinity of MMMs for CO2, MOF-based nanocomposites prepared by introducing specific functional groups/materials into MOFs have been utilized to combine the advantages of MOFs and other materials [20,21].