Mitigated Aging in a Defective Metal–Organic Framework Pillared Polymer of an Intrinsic Porosity Hybrid Membrane for Efficient Gas Separation

Abstract

Although polymers of intrinsic microporosity (PIMs) have been recognized as highly permeable membrane materials in gas separation, the physical aging phenomenon seriously affected their performance due to the collapse of micropores. In this work, we report an alternative approach to alleviate the physical aging of PIM-based membranes, as demonstrated by pillaring the PIM-1 membrane with defect-engineered metal–organic framework (MOF) nanoparticles. With excellent interfacial compatibility between the defective UiO-66-FA and PIM-1 by the formation of hydrogen-bond networks, the incorporated MOF nanoparticles acted as pillars of the resulting mixed matrix membranes (UiO-66-FA/PIM-1 MMM) to prevent the collapse of the micropores of the PIM-1 membrane and hence reduce its aging. Concurrently, defective MOFs in the polymer matrix endow the resulting MMMs with fast diffusion pathways and facilitate CO2 transport. Compared with the pristine PIM-1 membrane, UiO-66-FA/PIM-1 MMM displayed maintained CO2/N2 selectivity of about 23.1 but a sharp increased CO2 permeability from 3980 to 16,591 barrer. Only a 25% reduction in CO2 permeability was observed for the UiO-66-FA/PIM-1 MMM after 160 days of operation under the mixed-gas CO2/N2 separation conditions, which is less than the equivalent losses of 40 and 76% for the counterpart MOF-based hybrid membrane and PIM-1, respectively. Given that the performances of the resulting membranes far surpass the 2008 Robeson upper bound, this study may provide a feasible way for sustainable development of PIM-based MMMs in gas separation application.

Penetrant-induced plasticization in microporous polymer membranes

“…427 Work by Geng et al has also implemented defect-engineered UiO-66 nanoparticles as pillars to prevent the collapse of the PIM-1 structure and reduce physical aging. 428 In another recent study, Husna et al grafted UiO-66-NH 2 particles with PIM-1 to increase the overall compatibility of the filler into a PEBAX matrix. 429 The surface-modified MOF provided additional molecular transport channels for the MMM, yielding a CO 2 permeability of 247 with a CO 2 /N 2 selectivity of 56, improved mechanical properties and excellent aging resistance.…”

Mixed matrix metal–organic framework membranes for efficient CO2/N2 separation under humid conditions

“…6 Meanwhile, the mixed matrix membranes (MMMs) are usually used to address the present challenges facing polymer membranes, such as plasticization of polymeric materials and physical aging of glassy polymer membranes. 7,8 However, decreased separation performance and even worse unsatisfactory stability exposure to humid environment are fatal shortcomings of MOF materials in practical gas separation applications, which greatly hinders the industrial development of MMMOF membranes.…”

“…Among the various membrane materials, the mixed matrix metal–organic framework (MMMOF) membranes, combining processable polymers and screening MOF fillers, provide great potential to deploy MOF distinct sieving properties into polymer matrices for large‐scale and high performance membranes in the past few decades 6 . Meanwhile, the mixed matrix membranes (MMMs) are usually used to address the present challenges facing polymer membranes, such as plasticization of polymeric materials and physical aging of glassy polymer membranes 7,8 . However, decreased separation performance and even worse unsatisfactory stability exposure to humid environment are fatal shortcomings of MOF materials in practical gas separation applications, which greatly hinders the industrial development of MMMOF membranes.…”

Recent advances in the interfacial engineering of MOF-based mixed matrix membranes for gas separation

“…86 Moreover, the incorporation of defect-engineered UiO-66 particles into PIM-1 was carried out to prepare MMMs and the CO 2 /N 2 separation performance was improved due to the enhanced adhesion between the polymer and the defective MOF fillers. 19,87 As another renowned MOF material, defect-engineered ZIF-8 fillers have also been investigated in MMMs to enhance the gas separation performance. An et al synthesised defectengineered ZIF-8 nanoparticles using an alkyl amine modulator, which could coordinate with Zn 2+ ions (Fig.…”

“…A common way to prepare symmetric MMMs is through the solution blending method, which involves the preparation of polymer–MOF suspensions, membrane casting, and solvent removal. 14 Some examples of commonly used polymer matrices are PIM-1, 19,20 6FDA-polyimide, 15,18 Matrimid, 21 and Pebax. 22 To mitigate the agglomeration of MOF fillers, MOF particles were typically dispersed in a solvent prior to the addition of the polymer.…”