A Highly Ordered Nanoporous, Two-Dimensional Covalent Organic Framework with Modifiable Pores, and Its Application in Water Purification and Ion Sieving

Abstract

The preparation of membranes with high selectivity based on specific chemical properties such as size and charge would impact the efficiency of the world’s energy supply, the production of clean water, and many other separation technologies. We report a flexible synthetic protocol for preparing highly ordered two-dimensional nanoporous polymeric materials (termed covalent organic frameworks or COFs) that allow for placing virtually any function group within the nanopores. We demonstrate that membranes, fabricated with this new family of materials with carboxylated pore walls, are very water permeable, as well as highly charged and size selective.

Acid Exfoliation of Imine‐linked Covalent Organic Frameworks Enables Solution Processing into Crystalline Thin Films

“…Covalent organic frameworks (COFs) are an emerging class of porous crystalline polymers constructed from combinations of geometrically compatible monomers that are capable of polymerizing into two‐ or three‐dimensional networks . These materials have attracted significant attention over the past decade due to their high stability, accessible pores, and tunable functionality that demonstrate promise for applications including energy and gas storage, catalysis, and membrane‐based separation . However, most reported syntheses produce COFs as insoluble microcrystalline powders, a morphology that precludes many of these uses .…”

Covalent Organic Frameworks: Chemical Approaches to Designer Structures and Built‐In Functions

“…The phenazine linkage fuses the two monomers into a fully π‐conjugated system and constitutes the first example of an irreversible reaction for the synthesis of COFs. Phenazine‐linked COFs have been established as a platform to develop energy storage, photoenergy conversion, and catalytic systems . We have demonstrated the squaranine linkage for the synthesis of COFs by the condensation of amines and squaric acid (Figure ) .…”

Kovalente organische Gerüstverbindungen: chemische Ansätze für Designerstrukturen und integrierte Funktionen

“…Die Phenazinverknüpfung kondensiert die beiden Monomere zu einem vollständig π‐konjugierten System, dem ersten Beispiel einer irreversiblen Reaktion für die COF‐Synthese. Phenazinverknüpfte COFs bieten eine Plattform zur Entwicklung von Energiespeicher‐, Photoenergieumwandlungs‐ und Katalysesystemen . Wir konnten die Squaraninverknüpfung für die Synthese von COFs über die Kondensation von Amin und Quadratsäure einsetzen (Abbildung ) .…”

“…Phenazinverknüpfte COFs bieten eine Plattform zur Entwicklung von Energiespeicher-, Photoenergieumwandlungsund Katalysesystemen. [83,94] Wirk onnten die Squaraninverknüpfung fürdie Synthese von COFs über die Kondensation von Amin und Quadratsäure einsetzen (Abbildung 10). [77] Diese Verknüpfung liefert einen weiteren Ty pv on p-konjugierten COFs mit an den Porenwänden integrierten Zwitterioneneinheiten.…”