Increasing M₂(dobdc) Loading in Selective Mixed-Matrix Membranes: A Rubber Toughening Approach

Abstract

Mixed-matrix membranes (MMMs) were formed by incorporating M 2 (dobdc) (M = Mg, Ni; dobdc 4− = 2,5-dioxido-1,4-benzenedicarboxylate) metal−organic framework (MOF) nanoparticles in a series of poly(ether-imide) copolymers. Addition of the MOF nanoparticles improved the permeability of H 2 , N 2 , CH 4 , and CO 2 relative to the pure copolymer by increasing gas solubility and, in most cases, diffusivity. More limited improvements in diffusivity were observed for the more strongly adsorbing gases. Because of such transport considerations, improvements in permeability and selectivity were most pronounced for H 2 /CH 4 and H 2 /N 2 separations. Incorporation of a greater ether content within the copolymers led to the formation of defect-free MMMs by physically sealing polymer−MOF interfacial defects, allowing higher MOF loadings to be achieved. For Mg 2 (dobdc), selective, defect-free films could be formed with loadings of up to 51 wt %. However, at these high loadings, films became weak and brittle. The mechanical properties of the composite materials were therefore quantified by tensile tests and compared to those of the neat polymers used commercially for membrane film formation. High contents of flexible ether units and small MOF nanoparticle sizes were found to be necessary to form strong and ductile MMMs, although clear trade-offs exist between transport performance, MOF loading, and mechanical properties. These trade-offs are critically examined to evaluate the current limitations and potential benefits to forming M 2 (dobdc) MMMs using this rubber toughening approach.

Mixed-Matrix Membranes Formed from Imide-Functionalized UiO-66-NH2 for Improved Interfacial Compatibility

“…29,36−39 However, this polymer is highly rigid, as characterized by its glass-transition temperature of approximately 424 °C, and forming defect-free MMMs with polymers of limited intrinsic elasticity is notoriously challenging. 31 As hypothesized, the oligomer coating helped to form a uniform dispersion of oligomer–MOF hybrid particles in the polymer solution because chloroform is an excellent solvent for 6FDA–Durene, 40 and after the PSM reaction, both the polymer and surface of the MOF contain the same functionality. As shown in Figure 5a, suspensions of the polymer and PSM–MOF were visibly stable on the benchtop without any noticeable settling even after 24 h, enabling a facile formation of MMMs with a uniform MOF dispersion.…”

Performance of Mixed Matrix Membranes Containing Porous Two-Dimensional (2D) and Three-Dimensional (3D) Fillers for CO2 Separation: A Review

“…It was shown that the variation was mainly associated to the increase in CO 2 solubility, with minor effects on the gas diffusion through the selective layer. A similar study by Smith et al [ 127 ] proved that the addition of Mg 2 (dobdc) to 6FDA-Durene increased the permeability of CO 2 , N 2 , H 2 , and CH 4 due to the increase in diffusivity of the penetrants. It was observed that the MOF particles further increased the brittleness of the films due to densification.…”

Metal Organic Framework — Based Mixed Matrix Membranes for Carbon Dioxide Separation: Recent Advances and Future Directions

“… The performance of MOF-based MMMs [HKUST-1 (Car et al, 2006 ; Hu et al, 2010 ; Ge et al, 2013 ; Lin et al, 2016 ; Feijani et al, 2018 ; Chi et al, 2019 ); ZIF-7 (Li et al, 2013 ; Azizi and Hojjati, 2018 ); ZIF-8 (Ordoñez et al, 2010 ; Ban et al, 2015 ; Shahid et al, 2015 ; Dong et al, 2016a , b ; Jusoh et al, 2016 ; Lin et al, 2016 ; Anastasiou et al, 2018 ; Castro-Muñoz and Fíla, 2019 ; Yang et al, 2019 ; Zheng et al, 2019 ); UiO-66 (Nik et al, 2012 ; Dong et al, 2016b ; Shen et al, 2016 ; Satheeshkumar et al, 2018 ; Sutrisna et al, 2018 ; Tien-Binh et al, 2018 ; Zamidi Ahmad et al, 2018 ; Jia et al, 2019 ; Jiang et al, 2019 ; Katayama et al, 2019 ; Kim et al, 2019 ); MOF-5 (Perez et al, 2009 ); MIL-53 (Zornoza et al, 2011a ; Chen et al, 2013 ; Hsieh et al, 2014 ; Ahmadi Feijani et al, 2015 ; Feijani et al, 2015 ; Tien-Binh et al, 2015 ; Mubashir et al, 2018b ; Jiang et al, 2019 ); ZIF-90 (Bae et al, 2010 ); ZIF-11 (Safak Boroglu and Yumru, 2017 ); KAUST-7 (Chen K. et al, 2018 ); CuBDC (Cheng et al, 2017 ); Mg-MOF-74 (Bae and Long, 2013 ; Tien-Binh et al, 2016 ; Smith et al, 2018 ); Ni-MOF-74 (Bachman and Long, 2016 ; Yang et al, 2019 ); ZIF-94 (Etxeberria-Benavides et al, 2018 ); MIL-101 (Xin et al, 2015 ; Ma et al, 2016 ); Bio-MOF-1 (Ishaq et al, 2019 ); Fe(BTC) (Nabais et al, 2018 …”