A New Pentiptycene-Based Dianhydride and Its High-Free-Volume Polymer for Carbon Dioxide Removal

Versatile Porous Poly(arylene ether)s via Pd-Catalyzed C-O Polycondensation

Porous organic polymers (POPs) with strong covalent linkages between various rigid aromatic structural units having different geometries and topologies are reported. With inherent porosity, predictable structure, and tunable functionality, POPs have found utility in gas separation, heterogeneous catalysis, sensing, and water treatment. Poly(arylene ether)s (PAEs) are a family of high-performance thermoplastic materials with high glass-transition temperatures, exceptional thermal stability, robust mechanical properties, and excellent chemical resistance. These properties are desirable for development of durable POPs. However, the synthetic methodology for the preparation of these polymers has been mainly limited in scope to monomers capable of undergoing nucleophilic aromatic substitution (S_NAr) reactions. Herein, we describe a new general method using Pd-catalyzed C-O polycondensation reactions for the synthesis of PAEs. A wide range of new compositions and PAE architectures are now readily available using monomers with unactivated aryl chlorides and bromides. Specifically, monomers with conformational rigidity and intrinsic internal free volume are now used to create porous organic polymers with high molecular weight, good thermal stability, and porosity. The reported porous PAEs are solution processable and can be used in environmentally relevant applications including heavy-metal-ion sensing and capture.

Pushing Rubbery Polymer Membranes To Be Economic for CO2 Separation: Embedment with Ti3C2Tx MXene Nanosheets

Sustainable and energy-efficient molecular separation requires membranes with high gas permeability and selectivity. This work reports excellent CO₂ separation performance of self-standing and thin-film mixed matrix membranes (MMMs) fabricated by embedding 2D Ti₃C₂T_x MXene nanosheets in Pebax-1657. The CO₂/N₂ and CO₂/H₂ separation performances of the free-standing membranes are above Robeson's upper bounds, and the performances of the thin-film composite (TFC) membranes are in the target area for cost-efficient CO₂ capture. Characterization and molecular dynamics simulation results suggest that the superior performances of the Pebax-Ti₃C₂T_x membranes are due to the formation of hydrogen bonds between Ti₃C₂T_x and Pebax chains, leading to the creation of the well-formed galleries of Ti₃C₂T_x nanosheets in the hard segments of the Pebax. The interfacial interactions and selective Ti₃C₂T_x nanochannels enable fast and selective CO₂ transport. Enhancement of the transport properties of Pebax-2533 and polyurethane when embedded with Ti₃C₂T_x further supports these findings. The ease of fabrication and high separation performance of the new TFC membranes point to their great potential for energy-efficient CO₂ separation with the low cost of $29/ton separated CO₂.

Effects of synthesis methodology on microporous organic hyper-cross-linked polymers with respect to structural porosity, gas uptake performance and fluorescence properties

The structural characteristics of hyper-cross-linked polymers (HCPs) make them interesting for a wide variety of applications.

Pentiptycene-Based Polyurethane with Enhanced Mechanical Properties and CO2-Plasticization Resistance for Thin Film Gas Separation Membranes

The development of thin film composite (TFC) membranes offers an opportunity to achieve the permeability/selectivity requirements for optimum CO₂ separation performance. However, the durability and performance of thin film gas separation membranes are mostly challenged by weak mechanical properties and high CO₂ plasticization. Here, we designed new polyurethane (PU) structures with bulky aromatic chain extenders that afford preferred mechanical properties for ultra-thin-film formation. An improvement of about 1500% in Young's modulus and 600% in hardness was observed for pentiptycene-based PUs compared to the typical PU membranes. Single (CO₂, H₂, CH₄, and N₂) and mixed (CO₂/N₂ and CO₂/CH₄) gas permeability tests were performed on the PU membranes. The resulting TFC membranes showed a high CO₂ permeance up to 1400 GPU (10^-6 cm³(STP) cm^-2 s^-1 cmHg^-1) and the CO₂/N₂ and CO₂/H₂ selectivities of about 22 and 2.1, respectively. The enhanced mechanical properties of pentiptycene-based PUs result in high-performance thin membranes with the similar selectivity of the bulk polymer. The thin film membranes prepared from pentiptycene-based PUs also showed a twofold enhanced plasticization resistance compared to non-pentiptycene-containing PU membranes.