Porous organic polymer as fillers for fabrication of defect-free PIM-1 based mixed matrix membranes with facilitating CO2-transfer chain

Molecular Mobility and Gas Transport Properties of Mixed Matrix Membranes Based on PIM-1 and a Phosphinine Containing Covalent Organic Framework

Polymers with intrinsic microporosity (PIMs) are gaining attention as gas separation membranes. Nevertheless, they face limitations due to their pronounced physical aging. In this study, a covalent organic framework containing λ5-phosphinine moieties, CPSF-EtO, was incorporated as a nanofiller (concentration range 0-10 wt %) into a PIM-1 matrix forming dense films with a thickness of ca. 100 μm. The aim of the investigation was to investigate possible enhancements of gas transport properties and mitigating effects on physical aging. The incorporation of the nanofiller occurred on an nanoaggregate level with domains up to 100 nm, as observed by T-SEM and confirmed by X-ray scattering. Moreover, the X-ray data show that the structure of the microporous network of the PIM-1 matrix is changed by the nanofiller. As molecular mobility is fundamental for gas transport as well as for physical aging, the study includes dielectric investigations of pure PIM-1 and PIM-1/CPSF-EtO mixed matrix membranes to establish a correlation between the molecular mobility and the gas transport properties. Using the time-lag method, the gas permeability and the permselectivity were determined for N2, O2, CH4, and CO2 for samples with variation in filler content. A significant increase in the permeability of CH4 and CO2 (50% increase compared to pure PIM-1) was observed for a concentration of 5 wt % of the nanofiller. Furthermore, the most pronounced change in the permselectivity was found for the gas pair CO2/N2 at a filler concentration of 7 wt %.

Advancements in Gas Separation for Energy Applications: Exploring the Potential of Polymer Membranes with Intrinsic Microporosity (PIM)

Membrane-based Polymers of Intrinsic Microporosity (PIMs) are promising candidates for energy-efficient industrial gas separations, especially for the separation of carbon dioxide over methane (CO2/CH4) and carbon dioxide over nitrogen (CO2/N2) for natural gas/biogas upgrading and carbon capture from flue gases, respectively. Compared to other separation techniques, membrane separations offer potential energy and cost savings. Ultra-permeable PIM-based polymers are currently leading the trade-off between permeability and selectivity for gas separations, particularly in CO2/CH4 and CO2/N2. These membranes show a significant improvement in performance and fall within a linear correlation on benchmark Robeson plots, which are parallel to, but significantly above, the CO2/CH4 and CO2/N2 Robeson upper bounds. This improvement is expected to enhance the credibility of polymer membranes for CO2 separations and stimulate further research in polymer science and applied engineering to develop membrane systems for these CO2 separations, which are critical to energy and environmental sustainability. This review aims to highlight the state-of-the-art strategies employed to enhance gas separation performances in PIM-based membranes while also mitigating aging effects. These strategies include chemical post-modification, crosslinking, UV and thermal treatment of PIM, as well as the incorporation of nanofillers in the polymeric matrix.

Heteroatom-doped noble carbon-tailored mixed matrix membranes with ultrapermeability for efficient CO2 separation

Membranes with ultrapermeability for CO2 are desired for future large-scale carbon capture projects, because of their excellent separative productivity and economic efficiency. Herein, we demonstrate that a membrane with ultrapermeability for CO2 can be constructed by combining N/O para-doped noble carbons, C2NxO1-x, with high-permeability polymer PIM-1. The optimal PIM-1/C2NxO1-x membranes exhibit superior CO2 permeability (22110 Barrer) with a CO2/N2 selectivity of 15.5, and an unprecedented CO2 permeability of 37272 Barrer can be obtained after a PEG activation treatment, far surpassing the 2008 upper bound. Both broad experiments and molecular dynamics simulations reveal that the numerous ordered polar channels of C2NxO1-x and their excellent compatibility with PIM-1 are responsible for the superior CO2 separation performance of the membrane. Although this is the first study on C2N-type gas separation membranes, the outstanding results indicate that noble carbon building blocks may pave a new avenue to advance high-performance CO2 separation membranes.

Mixed Matrix Membranes Containing a Biphenyl-Based Knitting Aryl Polymer and Gas Separation Performance

Novel mixed matrix membranes (MMMs) were prepared using Matrimid (M), polysulfone (PSF) or polyphenylene oxide (PPO) as the continuous phase and a porous biphenyl-based knitting aryl polymer as a filler, synthesized through the Friedel–Craft reaction. The filler had little influence on the thermal and morphological properties of the membranes but affected the mechanical and gas transport properties, which were different depending on the type of matrix. Thus, in the case of MMMs based on Matrimid, the filler increased considerably the permeability to all gases, although no improvements in selectivity were achieved. A PSF-based MMM showed minor permeability increases, but not in all gases, while the selectivity was particularly improved for hydrogen separations. A PPO-based MMM did not exhibit variation in permeability nor in permselectivity with the addition of the filler.

Boosting gas separation performance and suppressing the physical aging of polymers of intrinsic microporosity (PIM-1) by nanomaterial blending

In recent decades, polymers of intrinsic microporosity (PIMs), especially the firstly introduced PIM-1, have been actively explored for various membrane-based separation purposes and widely recognized as the next generation membrane materials of choice for gas separation due to their ultra-permeable characteristics. Unfortunately, the polymers suffer substantially the negative impacts of physical aging, a phenomenon that is primarily noticeable in high free volume polymers. The phenomenon occurs at the molecular level, which leads to changes in the physical properties, and consequently the separation performance and membrane durability. This review discusses the strategies that have been employed to manage the physical aging issue, with a focus on the approach of blending with nanomaterials to give mixed matrix membranes. A detailed discussion is provided on the types of materials used, their inherent properties, the effects on gas separation performance, and their benefits in the suppression of the aging problem.

Thiophene-embedded conjugated microporous polymers for photocatalysis

“Bottom-up” embedding of thiophene derivatives into CMPs for highly efficient heterogeneous photocatalysis is reported.

Interfacial Property Modulation of PIM-1 through Polydopamine-Derived Submicrospheres for Enhanced CO2/N2 Separation Performance

Polydopamine-modified additives have been thus far widely used in the mixed matrix membranes (MMMs) for gas separation. However, very few reports focus on the polydopamine alone and investigate its contribution to the gas separation performance. Herein, the polydopamine-derived submicrospheres (PDASS) were paired with polymers of intrinsic microporosity (PIM-1) to fabricate high-performance gas separation membranes, through which the effects of PDASS on gas permeability and CO₂/N₂ separation performance were systematically investigated. The addition of PDASS provides a 1.6-fold enhancement in CO₂/N₂ selectivity together with acceptable gas permeability as compared to the original polymeric membrane. Such enhanced separation behavior is supposed to stem from the densified membrane microstructure induced by the strong intermolecular interactions between PIM-1 and PDASS (i.e., charge transfer, π-π stacking, and hydrogen bonding). Importantly, the physical aging behavior, as judged by gas permeability, is retarded for PIM/PDASS membranes after 4 months of testing.