Polyetheramine–polyhedral oligomeric silsesquioxane organic–inorganic hybrid membranes for CO2/H2 and CO2/N2 separation

Tailoring Crosslinked Polyether Networks for Separation of CO2 from Light Gases

Crosslinked poly(ethylene oxide) or poly(ethylene glycol) (PEG) is an ideal membrane material for separation of CO₂ from light gases (e.g., H₂ , N₂ , O₂ , CH₄ etc). In these membranes, crosslinking is used as a tool to suppress crystallinity of the PEG segments. In spite of the extensive effort to develop crosslinked PEG membranes in the last two decades, it remains a challenge to establish the structure-property relationships. This paper points out the fundamental limitations to correlate the chain topology of a network with the gas permeation mechanism. While a quantitative comparison of the molecular weight between crosslinks of networks and gas permeation mechanism reported by different research groups is challenging, effort is made to draw a qualitative picture. In this review, a focus is also put on the progress of utilization of dangling chain fractions to tailor the gas permeation behavior of PEG networks.

Improving the Selectivity of ZIF-8/Polysulfone-Mixed Matrix Membranes by Polydopamine Modification for H2/CO2 Separation

Gas separation membranes are essential for the capture, storage, and utilization (CSU) of CO₂, especially for H₂/CO₂separation. However, both glassy and rubbery polymer membranes lead a relatively poor selectivity for H₂/CO₂ separation because the differences in kinetic diameters of these gases are small. The present study establishing the mixed matrix membranes (MMMs) consist of a nano-sized zeolitic imidazolate frameworks (ZIF-8) blended with the polysulfone (PSf) asymmetric membranes. The gas transport properties (H₂, CO₂, N₂, and CH₄) of MMMs with a ZIF-8 loading up to 10 wt% were tested and showing significant improvement on permeance of the light gases (e.g., H₂ and CO₂). Moreover, the depositional polydopamine (PDA) layer further enhanced the ideal H₂/CO₂ selectivity, and the PDA-modified MMMs approach the Robeson upper bound of H₂/CO₂ separation membranes. Hence, the PDA post-modification strategy can effectively repair the defects of MMMs and improved the H₂/CO₂selectivity.

Synthesis and Characterization of Novel Nanoporous Gl-POSS-Branched Polymeric Gas Separation Membranes

Novel nanoporous Gl-POSS-branched polymers based on the macroinitiator of anionic nature, 2,4-toluene diisocyanate, and octaglycidyl polyhedral oligomeric silsesquioxane (Gl-POSS) were obtained as gas separation membranes. The synthesis of polymers was carried out using various loads of Gl-POSS. It was found that the main reaction proceeding with 2,4-toluene diisocyanate is the polyaddition, accompanied by the isocyanate groups opening of the carbonyl part. This unusual opening of isocyanate groups leads to the formation of coplanar acetal nature polyisocyanates (O-polyisocyanate). The terminal O-polyisocyanate links initiate the subsequent opening of the epoxide rings in Gl-POSS. As a result, Gl-POSS serves as a hard and bulky branching agent and creates the specific framing supramolecular structure, which leads to the formation of nanopores in the polymer, where the flexible polyether components are located inside the cavities. Thermal, mechanical, physical, and chemical properties of the obtained polymers were studied at various Gl-POSS contents in the polymer matrix. It was found that these polymers show high selectivity of gas transport properties for pure ammonia relative to nitrogen and hydrogen at ambient temperature. Measurements showed that the gas permeability coefficients and the values of ideal selectivity were in a non-additive dependence to the Gl-POSS content.

CO₂ Separation in Nanocomposite Membranes by the Addition of Amidine and Lactamide Functionalized POSS® Nanoparticles into a PVA Layer

In this article, we studied two different types of polyhedral oligomeric silsesquioxanes (POSS^®) functionalized nanoparticles as additives for nanocomposite membranes for CO₂ separation. One with amidine functionalization (Amidino POSS^®) and the second with amine and lactamide groups functionalization (Lactamide POSS^®). Composite membranes were produced by casting a polyvinyl alcohol (PVA) layer, containing either amidine or lactamide functionalized POSS^® nanoparticles, on a polysulfone (PSf) porous support. FTIR characterization shows a good compatibility between the nanoparticles and the polymer. Differential scanning calorimetry (DSC) and the dynamic mechanical analysis (DMA) show an increment of the crystalline regions. Both the degree of crystallinity (Xc) and the alpha star transition, associated with the slippage between crystallites, increase with the content of nanoparticles in the PVA selective layer. These crystalline regions were affected by the conformation of the polymer chains, decreasing the gas separation performance. Moreover, lactamide POSS^® shows a higher interaction with PVA, inducing lower values in the CO₂ flux. We have concluded that the interaction of the POSS^® nanoparticles increased the crystallinity of the composite membranes, thereby playing an important role in the gas separation performance. Moreover, these nanocomposite membranes did not show separation according to a facilitated transport mechanism as expected, based on their functionalized amino-groups, thus, solution-diffusion was the main mechanism responsible for the transport phenomena.

Performance of Nanocomposite Membranes Containing 0D to 2D Nanofillers for CO₂ Separation: A Review

Membrane technology has the potential to be an eco-friendly and energy-saving solution for the separation of CO₂ from different gaseous streams due to the lower cost and the superior manufacturing features. However, the performances of membranes made of conventional polymers are limited by the trade-off between the permeability and selectivity. Improving the membrane performance through the addition of nanofillers within the polymer matrix offers a promising strategy to achieve superior separation performance. This review aims at providing a complete overview of the recent advances in nanocomposite membranes for enhanced CO₂ separation. Nanofillers of various dimensions and properties are categorized and effects of nature and morphology of the 0D to 2D nanofillers in the corresponding nanocomposite membranes of different polymeric matrixes are discussed with regard to the CO₂ permeation properties. Moreover, a comprehensive summary of the performance data of various nanocomposite membranes is presented. Finally, the advantages and challenges of various nanocomposite membranes are discussed and the future research and development opportunities are proposed.

Visualization and characterization of interfacial polymerization layer formation

We present a microfluidic platform to visualize the formation of free-standing films by interfacial polymerization. A microfluidic device is fabricated, with an array of micropillars to stabilize an aqueous-organic interface that allows a direct observation of the films formation process via optical microscopy. Three different amines are selected to react with trimesoyl chloride: piperazine, JEFFAMINE(®)D-230, and an ammonium functionalized polyhedral oligomeric silsesquioxane. Tracking the formation of the free-standing films in time reveals strong effects of the characteristics of the amine precursor on the morphological evolution of the films. Piperazine exhibits a rapid reaction with trimesoyl chloride, forming a film up to 20 μm thick within half a minute. JEFFAMINE(®)D-230 displays much slower film formation kinetics. The location of the polymerization reaction was initially in the aqueous phase and then shifted into the organic phase. Our in situ real-time observations provide information on the kinetics and the changing location of the polymerization. This provides insights with important implications for fine-tuning of interfacial polymerizations for various applications.

Synergistic interactions between POSS and fumed silica and their effect on the properties of crosslinked PDMS nanocomposite membranes

A facile strategy for the synthesis of binary fumed silica–POSS nanofillers based nanocomposite membranes was developed.

Rational molecular design of PEOlated ladder-structured polysilsesquioxane membranes for high performance CO2 removal

By selectively introducing PEO groups into the ladder-structured polysilsesquioxane, PEO crystallization was suppressed, allowing for the exceptional CO₂ separation performance.

Design and characterization of liquidlike POSS-based hybrid nanomaterials synthesized via ionic bonding and their interactions with CO2

Liquidlike nanoparticle organic hybrid materials (NOHMs) were designed and synthesized by ionic grafting of polymer chains onto nanoscale silica units called polyhedral oligomeric silsesquioxane (POSS). The properties of these POSS-based NOHMs relevant to CO2 capture, in particular thermal stability, swelling, viscosity, as well as their interactions with CO2, were investigated using thermogravimetric analyses, differential scanning calorimetry, and NMR and ATR FT-IR spectroscopies. The results indicate that POSS units significantly enhance the thermal stability of the hybrid materials, and their porous nature also contributes to the overall CO2 capture capacity of NOHMs. The viscosity of the synthesized NOHMs was comparable to those reported for ionic liquids, and rapidly decreased as the temperature increased. The sorption of CO2 in POSS-based NOHMs also reduced their viscosities. The swelling behavior of POSS-based NOHMs was similar to that of previously studied nanoparticle-based NOHMs, and this generally resulted in less volume increase in NOHMs compared to their corresponding polymers for the same amount of CO2 loading.