Microporous Organic Polyimides for CO₂ and H₂O Capture and Separation from CH₄ and N₂ Mixtures: Interplay between Porosity and Chemical Function

Abstract

Porous polyimides have been considered to be a promising material class for gas capture and sequestration, leading to the synthesis of a substantial number of individual networks with noteworthy sorption properties. In spite of these efforts, the vision of a chemical control of adsorption and desorption of small molecules, in particular, for the competing uptake of technical relevant gas mixtures, is still hardly investigated. Here, we present a systematic study of five new polyimide networks based on a set of linkers with chemical functionalities covering the full range from hydrophobic to hydrophilic interactions. The corresponding microporous organic polyimides (MOPI-I to -V) were synthesized successfully based on a condensation reaction between amino and anhydride linker molecules in m-cresol at high temperatures, resulting in cross-linking degrees beyond 95% in all cases. Argon and carbon dioxide isotherms reveal surface areas up to 940 m2/g with ultramicroporosity, about 50% microporosity and high thermal stabilities under air with decomposition temperatures up to 480 °C. Sorption screening for variable temperatures revealed remarkable uptakes for carbon dioxide up to 3.8 mmol/g and water vapor up to 19.5 mmol/g combined with a smooth gate opening around 0.25 p/p 0 for MOPI-IV. In contrast, for MOPI-V the water vapor uptake decreases down to 7 mmol/g. Interestingly, the trend of the selectivities calculated by IAST and Henry does not correlate with the uptake behavior. For instance, MOPI-I and MOPI-III exhibit with 78 and 13 the highest CO2 over N2 and CH4 Henry selectivities, although their CO2 uptake is around 3.0 mmol/g. In total, we attribute the sorption properties for this class of materials mainly to the void size and shape within the ultramicroporous region. The chemical environment of the surfaces seems to have little influence on the uptake and a stronger effect on the separation behavior.

Advances in Porous Organic Polymers for Efficient Water Capture

“…Apart from imine-linked porousn etworks, Senker et al [73] also reported as eries of microporous organic polyimides (Figure 12 a), which incorporatearange of bridging groups including diphenylsulfone (MOPI-I), diphenylether (MOPI-II), benzophenone (MOPI-III), bicycle[2,2,2]oct-7-en (MOPI-IV), and hexafluoro-2,2-diphenylpropane (MOPI-V). All of the water sorption isotherms (Figure 12 b) showedagradual rise throughout the entire relative pressure range,i ndicating that the sorbents contain hydrophilic sites.…”

“…(b) Adsorption (closed symbols) and desorption isotherms (opensymbols) of water vapor for MOPIs. Reprinted with permission from Ref [73]…”

Microporous Organic Polymers Based on Hyper‐Crosslinked Coal Tar: Preparation and Application for Gas Adsorption

“…Gas adsorption is a fundamental unit operation that is important for chemical engineering, greenhouse‐gas capture, and pollution treatment . Both chemical and physical adsorption techniques have been employed in practical applications .…”

“…Gas adsorption is af undamental unit operation that is important for chemicale ngineering, greenhouse-gas capture, and pollutiont reatment. [1][2][3] Both chemical andp hysicala dsorption techniques have been employed in practical applications. [4,5] For example, the traditional methodf or fixing CO 2 is to bubble the mixed gases through aqueous alkanolamine.…”

A Microporous Covalent–Organic Framework with Abundant Accessible Carbonyl Groups for Lithium‐Ion Batteries

“…Covalent-organic frameworks (COFs) have attracted extensive interests in gas separation, [12] electrolyte membrane, [13] and electrochemical devices recently. [14,15] Rational design of COFs is effective to realize their versatile functionalities and applications.B yt uning the functional groups, Jiangsg roup reported aC OF from hexaazatrinaphthalene and diethynylbenzene to deliver acapacity of 147 mAh g À1 .…”