Rapid, Low Temperature Formation of Imine-Linked Covalent Organic Frameworks Catalyzed by Metal Triflates

Abstract

Imine-linked two-dimensional covalent organic frameworks (2D COFs) are crystalline polymer networks with enhanced stability compared to boronate ester-linked systems and with broad monomer scope. They are traditionally prepared by condensing polyfunctional aldehydes and amines at elevated temperature in a mixture of organic solvents and aqueous CHCOH, which catalyzes imine formation and exchange. Here we employ metal triflates, which are water-tolerant Lewis acids, to accelerate 2D imine-linked COF synthesis and improve their materials quality. Low catalyst loadings provide crystalline polymer networks in nearly quantitative yields. These conditions are demonstrated for several COFs, including heteroatom-containing systems of interest for optoelectronic applications.

Ultrastable Imine‐Based Covalent Organic Frameworks for Sulfuric Acid Recovery: An Effect of Interlayer Hydrogen Bonding

“…[4] We have already attempted to overcome the stability issues in COFs,b yi ntroducing the enol to keto tautomerization phenomenon during the framework crystallization. [6] However, for the widespread implementation of such chemically stable imine based COFs,t he synthetic process should:1 )bed evoid of toxic solvents or synthetic difficulty, [5] 2) be rapid and easily scalable (unlike the traditional solvothermal process), [5,7] and 3) provide the opportunity to process the as-synthesized COFs into pellets,beads as well as membranes keeping their properties intact. [4a, 5] However,t his idea is entirely restricted to b-ketoenamine COFs,w hich provides minimal substrate scope and thus are limited in their widespread exploration.…”

Highly Crystalline and Semiconducting Imine‐Based Two‐Dimensional Polymers Enabled by Interfacial Synthesis

“…Lewis Acid Catalyst Mediated Synthesis of PI‐2DP : Besides the reaction temperature, catalysts play a crucial role in the rate‐limiting step of converting amorphous imine polymer network into crystalline framework . Thereby, a small amount of Lewis acid metal triflate catalyst Yb(OTf) 3 was added into the water phase.…”

“…Lewis Acid Catalyst Mediated Synthesis of PI-2DP: Besides the reaction temperature,catalysts play acrucial role in the rate-limiting step of converting amorphous imine polymer network into crystalline framework. [23] Thereby, asmall amount of Lewis acid metal triflate catalyst Yb(OTf) 3 was added into the water phase.T he subsequent interfacial polymerization at 50 8 8Cy ielded aP I-2DP 1 film with as ubstantial increase in average crystalline domain size up to % 150 nm (Figure 5a), which is larger than that with acetic acid as catalyst ( Figure S8) and without catalyst ( Figure S6). Here,w ater-tolerant Yb(OTf) 3 can efficiently catalyze imine formation and transamination reaction, [24] thus enabling the enhancement of the crystallinity of 2D polyimine.…”

Kovalente organische Netzwerke und Käfigverbindungen: Design und Anwendungen von polymeren und diskreten organischen Gerüsten

“…[85,86] Brønsted-Säuren wie AcOH [93][94][95] oder Metalltriflate als wasserverträgliche Lewis-Säuren [196] werden typischerweise zur Katalyse der Iminbildung eingesetzt. Sowohl die präzise Kontrolle der nanoskaligen Morphologie als auch verlässliche Vorschriften fürd ie Prozessierung der Materialien sind Schlüsselfaktoren fürd ie Entwicklung von zukünftigen Anwendungen dieser Strukturen.…”