Thermally cross-linked diaminophenylindane (DAPI) containing polyimides for membrane based gas separations

Intrinsically Microporous Polyimides Derived from 2,2'-Dibromo-4,4',5,5'-bipohenyltetracarboxylic Dianhydride for Gas Separation Membranes

This work aims to expand the structure-property relationships of bromo-containing polyimides and the influence of bromine atoms on the gas separation properties of such materials. A series of intrinsically microporous polyimides were synthesized from 2,2'-dibromo-4,4',5,5'-bipohenyltetracarboxylic dianhydride (Br-BPDA) and five bulky diamines, (7,7'-(mesitylmethylene)bis(8-methyldibenzo[b,e][1,4]dioxin-2-amine) (MMBMA), 7,7'-(Mesitylmethylene)bis(1,8-dimethyldibenzo[b,e][1,4] dioxin-2-amine) (MMBDA), 4,10-dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine-2,8-diamine (TBDA1), 4,10-dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine-3,9-diamine (TBDA2), and (9R,10R)-9,10-dihydro-9,10-[1,2]benzenoanthracene-2,6-diamine (DAT). The Br-BPDA-derived polyimides exhibited excellent solubility, high thermal stability, and good mechanical properties, with their tensile strength and modulus being 59.2-109.3 MPa and 1.8-2.2 GPa, respectively. The fractional free volumes (FFVs) and surface areas (SBET) of the Br-BPDA-derived polyimides were in the range of 0.169-0.216 and 211-342 m2 g-1, following the order of MMBDA > MMBMA > TBDA2 > DAT > TBDA1, wherein the Br-BPDA-MMBDA exhibited the highest SBET and FFV and thus highest CO2 permeability of 724.5 Barrer. Moreover, Br-BPDA-DAT displayed the best gas separation performance, with CO2, H2, O2, N2, and CH4 permeabilities of 349.8, 384.4, 69.8, 16.3, and 19.7 Barrer, and H2/N2 selectivity of 21.4. This can be ascribed to the ultra-micropores (<0.7 nm) caused by the high rigidity of Br-BPDA-DAT. In addition, all the bromo-containing polymers of intrinsic microporosity membranes exhibited excellent resistance to physical ageing.

Fabrication, Facilitating Gas Permeability, and Molecular Simulations of Porous Hypercrosslinked Polymers Embedding 6FDA-Based Polyimide Mixed-Matrix Membranes

Novel polymers applied in economic membrane technologies are a perennial hot topic in the fields of natural gas purification and O₂ enrichment. Herein, novel hypercrosslinked polymers (HCPs) incorporating 6FDA-based polyimide (PI) MMMs were prepared via a casting method for enhancing transport of different gases (CO₂, CH₄, O₂, and N₂). Intact HCPs/PI MMMs could be obtained due to good compatibility between the HCPs and PI. Pure gas permeation experiments showed that compared with pure PI film, the addition of HCPs effectively promotes gas transport, increases gas permeability, and maintains ideal selectivity. The permeabilities of HCPs/PI MMMs toward CO₂ and O₂ were as high as 105.85 Barrer and 24.03 Barrer, respectively, and the ideal selectivities of CO₂/CH₄ and O₂/N₂ were 15.67 and 3.00, respectively. Molecular simulations further verified that adding HCPs was beneficial to gas transport. Thus, HCPs have potential utility in fabrication of MMMs for facilitating gas transport in the fields of natural gas purification and O₂ enrichment.

Thermally stimulated cascade reaction polymer membranes: a promising strategy for an increased hydrogen and propylene purification performance

A thermally stimulated cascade of reactions in solid-state of tailored polyimides was developed with the aim of lowering the target temperature for the final reaction step towards a polybenzoxazole and improvement of the gas separation performance.

Constructing Strong Interfacial Interactions under Mild Conditions in MOF-Incorporated Mixed Matrix Membranes for Gas Separation

Although mixed matrix membranes (MMM) possess remarkably improved gas separation performance compared to traditional polymeric membranes, membrane stability including CO₂ plasticization and aging is still a serious issue due to the existence of interfacial defects. In this work, we report an efficient and less destructive route to cross-link the MOFs/polyimide (PI) MMM, where amine group-functionalized MOF (NH₂-UiO-66) nanoparticles are thermally cross-linked with a carboxylic acid-functionalized PI (COOH-PI) matrix to form an amide bond at the interface at 150 °C under vacuum condition. Such a chemical cross-linking strategy conducted at a relatively mild condition improves membrane stability greatly while ensuring that the membrane structure is not destroyed. The resulting cross-linked MMM achieves enhanced mechanical strength with higher Young's modulus than a pristine polymer membrane. The CO₂ antiplasticization pressure of the MMM after cross-linking is enhanced by 200% from ∼10 to >30 bar and the CO₂ permeability of MMM only drops slightly from 995 to 735 Barrer after 450 days. At the same time, the separation performance of H₂/CH₄ gas pair surpasses the 2008 upper bound and that of CO₂/CH₄ gas pair nearly approaches the 2008 upper bound. The cross-linking strategy used herein provides a feasible and effective route for improving membrane stability and membrane performance in the MMM system for gas separation.

Crosslinked porous polyimides: structure, properties and applications

Porous polyimides (pPIs) represent a fascinating class of porous organic polymers (POPs). Here the properties and functions of amorphous and crystalline pPIs are reviewed, and applications contributing to solutions to global challenges highlighted.