Precision Construction of 2D Heteropore Covalent Organic Frameworks by a Multiple‐Linking‐Site Strategy

Abstract

Integrating different kinds of pores into one covalent organic framework (COF) endows it with hierarchical porosity and thus generates a member of a new class of COFs, namely, heteropore COFs. Whereas the construction of COFs with homoporosity has already been well developed, the fabrication of heteropore COFs still faces great challenges. Although two strategies have recently been developed to successfully construct heteropore COFs from noncyclic building blocks, they suffer from the generation of COF isomers, which decreases the predictability and controllability of construction of this type of reticular materials. In this work, this drawback was overcome by a multiple-linking-site strategy that offers precision construction of heteropore COFs containing two kinds of hexagonal pores with different shapes and sizes. This strategy was developed by designing a building block in which double linking sites are introduced at each branch of a C -symmetric skeleton, the most widely used scaffold to construct COFs with homogeneous porosity. This design provides a general way to precisely construct heteropore COFs without formation of isomers. Furthermore, the as-prepared heteropore COFs have hollow-spherical morphology, which has rarely been observed for COFs, and an uncommon staggered AB stacking was observed for the layers of the 2D heteropore COFs.

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

“…A [ C 2 + C 2 ] diagram can also form a kagome skeleton (Figure b) as well as the rhombic topology . A three‐branched C 2 ‐ or C 3 ‐symmetric unit with a C 2 ‐symmetric unit forms kagome structures with a central hexagon surrounded by six irregular hexagons (Figure c,d) …”

“…[48][49][50] A three-branched C 2 -orC 3 -symmetric unit with a C 2 -symmetric unit forms kagome structures with ac entral hexagon surrounded by six irregular hexagons (Figure 5c,d). [51,52]…”

Kovalente organische Gerüstverbindungen: chemische Ansätze für Designerstrukturen und integrierte Funktionen

“…Auch das [ C 2 + C 2 ]‐Diagramm kann, neben der rhombischen Topologie, Kagome‐Gerüste bilden (Abbildung b) . Eine C 2 ‐ oder C 3 ‐symmetrische Einheit bildet zusammen mit einer C 2 ‐symmetrischen Einheit Kagome‐Strukturen mit einem zentralen Sechseck, das von sechs unregelmäßigen Sechsecken umgeben ist (Abbildung c,d) …”

“…[48][49][50] Eine C 2 -o der C 3 -symmetrische Einheit bildet zusammen mit einer C 2symmetrischen Einheit Kagome-Strukturen mit einem zentralen Sechseck, das von sechs unregelmäßigen Sechsecken umgeben ist (Abbildung 5c,d). [51,52] Eine allgemeine Strategie dafürw urde über Mehrkomponentendiagramme eingeführt (Abbildung 6). [53] Ein C 3symmetrischer Knoten in Kombination mit zwei C 2 -symmetrischen Linkern bildet hexagonale Gerüste,b ei denen die Gerüste eine anisotrope Flächenbedeckung bilden und die hexagonalen Poren eine spezifisch verformte Gestalt aufweisen (Abbildung 6a).…”

Postsynthetic Covalent Modification in Covalent Organic Frameworks

“…Meanwhile, the wider availability of organic building block possible to employ in COFs synthesis lead the micro‐ to mesoporous COFs with 2D and 3D dimensions have been designed so far ,,. Moreover, heteropores‐type COFs have also been realized recently demonstrating the great potentials in size selective separation and conversion ,. In addition, the design structure in COFs should satisfy the rigidity issue to establish long‐order and defined pore structure (e. g. 2D or 3D tetragonal or hexagonal shapes) as final framework.…”