Thiophene-based covalent organic frameworks

Abstract

We report the synthesis and characterization of covalent organic frameworks (COFs) incorporating thiophene-based building blocks. We show that these are amenable to reticular synthesis, and that bent ditopic monomers, such as 2,5-thiophenediboronic acid, are defect-prone building blocks that are susceptible to synthetic variations during COF synthesis. The synthesis and characterization of an unusual charge transfer complex between thieno[3,2-b]thiophene-2,5-diboronic acid and tetracyanoquinodimethane enabled by the unique COF architecture is also presented. Together, these results delineate important synthetic advances toward the implementation of COFs in electronic devices.electronic materials | polymers | porous materials C ovalent organic frameworks (COFs) have emerged as an important class of polymeric crystalline materials with potential applications that complement those of metal organic frameworks (MOFs) (1-7). In particular, 2D COFs exhibit unique architectures wherein the monomers that make up their 2D layers stack almost perfectly into infinite 1D columns that are ideal for charge and exciton transport (6-12). Such electronic properties are particularly difficult to engineer in microporous MOFs, where high charge mobility and conductivity have only recently been demonstrated (13-15). Despite their layered structures, the typical hexagonal or square lattices of 2D COFs exhibit large 1D channels with well-defined pores that can be subject to reticular chemistry and postsynthetic modification (16,17), and where complementary donor or acceptor molecules may in principle be inserted. Clearly, the unprecedented combination of high surface area, crystallinity, chemical and pore size tunability, and unique molecular architecture make COFs tantalizing targets for a new generation of electronic devices, including sustainable batteries, field-effect transistors, and photovoltaics. The first steps toward such applications must involve the incorporation of electroactive monomers within the COFs. This has been beautifully exemplified by the insertion of porphyrins (18), phthalocyanines (9), pyrene (8), naphthalenetetracarboxydiimide (19), and benzothiadiazole (20) in such materials. Notably, however, one of the most popular monomers in conductive organic polymers, thiophene, has not been incorporated in COFs thus far. Herein, we report the synthesis and characterization of thiophene-based COFs, including materials made from thiophene-, bithiophene-, and thienothiophene-diboronic acids. We also advance a hypothesis regarding the more general synthetic tractability of COFs made from bent ligands. Finally, we show that p-type COFs are amenable to doping with electron acceptors and report an unusual charge-transfer complex with tetracyanoquinodimethane (TCNQ). Results and DiscussionWe prepared thiophene-based COF (T-COFs) under conditions mimicking those used for the synthesis of the prototypical COF-5. Thus, condensation of 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) with 2,5-thiophenediboronic acid (H 4 TDB) (21) in...

Function-led design of new porous materials

“…There are also recent studies that demonstrate new possibilities for porous solids (105)(106)(107)(108)(109)(110)(111)(112)(113)(114)(115) where the advantages over materials such zeolites are perhaps more clear-cut. For example, in battery and supercapacitor technologies, new porous solids (114) will be competing instead with materials such as graphite and graphene.…”

“…In particular, carbon nitride (103) and carbon nitride composite materials (104) show promise as metal-free catalysts for the photochemical splitting of water, although those materials are not inherently porous. Extended conjugation is not a typical property of zeolites or MOFs, but this can be achieved in conjugated microporous polymers (22) and in some COFs (105)(106)(107). The modular design of improved porous organic photocatalysts-for example, by using "band gap engineering" strategies (24) to allow more effective adsorption of the available solar spectrum-is a design strategy for the future, as exemplified recently for porous polypyrene materials for photochemical hydrogen evolution (25).…”

“…Porous COFs (105)(106)(107) and MOFs (113) have potential in organic electronics, and porous conjugated microporous polymers are promising supercapacitors (114). Solutionprocessable porous organic solids have been incorporated into sensors (115).…”

An Efficient Approach to Octabromophenylethyl‐Functionalized Cage Silsesquioxane and Its Use in Constructing Hybrid Porous Materials

“…Thus, cage polymer 1 is an amorphous porous polymer according to PXRD and FE-SEM. Optical characteristics of porous polymers extend their applications greatly in light harvesting, [13,41] sensors, [42] photocatalysts, [43] electronic devices, [44] and the detection of chemicals, [45] and this aroused our interest in investigating the fluorescent and ultraviolet features of cage polymer 1. As shown in Figure 8, the UV/Vis and luminescence spectra of cage polymer 1 were measured.…”

Recent Progress in the Fabrication of Low Dimensional Nanostructures via Surface-Assisted Transforming and Coupling

“…Unlike the reaction that occurred in solution, fabricating low dimensional COF at the liquid/solid or gas/solid interface through self-condensation of boronic acids is a novel method to form a series of nanomaterials equipped with functional characteristics such as sensing [38,39], energy storage [40], optoelectronic devices [41,42], and catalysis [43,44]. The building blocks of the condensation equipped with more than two functional groups, hydroxide radical, is a basic precondition to trigger the reaction, and the ambient environment around the reaction monomers can obviously decide the quality of the surface covalent organic framework (SCOF).…”