Flexible three-dimensional diacetylene functionalized covalent organic frameworks for efficient iodine capture

Multivariate Flexible Metal-Organic Frameworks and Covalent Organic Frameworks

Precise control of the void environment, achieved through multiple functional groups and enhanced by structural adaptations to guest molecules, stands at the forefront of scientific inquiry. Flexible multivariate open framework materials (OFMs), including covalent organic frameworks and metal-organic frameworks, meet these criteria and are expected to play a crucial role in gas storage and separation, pollutant removal, and catalysis. Nevertheless, there is a notable lack of critical evaluation of achievements in their chemistry and future prospects for their development or implementation. To provide a comprehensive historical context, the initial discussion explores into the realm of "classical" flexible OFMs, where their origin, various modes of flexibility, similarities to proteins, advanced tuning methods, and recent applications are explored. Subsequently, multivariate flexible materials, the methodologies involved in their synthesis, and horizons of their application are focussed. Furthermore, the reader to the concept of spatial distribution is introduced, providing a brief overview of the latest reports that have contributed to its elucidation. In summary, the critical review not only explores the landscape of multivariate flexible materials but also sheds light on the obstacles that the scientific community must overcome to fully unlock the potential of this fascinating field.

Topochemical cross-linking of diacetylene in a highly interpenetrated three-dimensional covalent organic framework

Topochemical polymerization is a highly promising and effective method for constructing complex three-dimensional structures and functionalized polymers. Herein, we present for the first time a topochemical reaction of diacetylene within a meticulously designed covalent organic framework (ZNUC-1). Our experimental results revealed that ZNUC-1 underwent a 1,4-addition reaction under thermal induction, forming an ene-yne-conjugated structure.

Expanding Olefin-Linked Covalent Organic Frameworks toward Selective Photocatalytic Oxidation of Organic Sulfides

Olefin-linked covalent organic frameworks (COFs) have exhibited great potential in visible-light photocatalysis. In principle, expanding fully conjugated COFs can facilitate light absorption and charge transfer, leading to improved photocatalysis. Herein, three olefin-linked COFs with the same topology are synthesized by combining 2,4,6-trimethyl-1,3,5-triazine (TMT) with 1,3,5-triformylbenzene (TFB), 1,3,5-tris(4-formylphenyl)benzene (TFPB), and 1,3,5-tris(4-formylphenylethynyl)benzene (TFPEB), namely, TMT-TFB-COF, TMT-TFPB-COF, and TMT-TFPEB-COF, respectively. From TMT-TFB-COF to TMT-TFPB-COF, expanding phenyl rings provides only limited expansion for π-conjugation due to the steric effect of structural twisting. However, from TMT-TFPB-COF to TMT-TFPEB-COF, the insertion of acetylenes eliminates the steric effect and provides more delocalized π-electrons. As such, TMT-TFPEB-COF exhibits the best optoelectronic properties among these three olefin-linked COFs. Consequently, the photocatalytic performance of TMT-TFPEB-COF is much better than those of TMT-TFB-COF and TMT-TFPB-COF on the oxidation of organic sulfides into sulfoxides with oxygen. The desirable reusability and substrate compatibility of the TMT-TFPEB-COF photocatalyst are further confirmed. The selective formation of organic sulfoxides over TMT-TFPEB-COF under blue light irradiation proceeds via both electron- and energy-transfer pathways. This work highlights a rational design of expanding the π-conjugation of fully conjugated COFs toward selective visible-light photocatalysis.

One-step synthesis of a benzothiadiazole-based nonbranching functionalized covalent organic framework and its application in efficient removal of Hg2

In recent years, a variety of adsorbents have been developed for Hg2+ removal. However, these adsorbents are unsatisfactory for adsorption due to narrow and irregular pore channels or poor adsorption capacity and low stability. Therefore, it is worth exploring a porous Hg2+ adsorbent material with high adsorption performance and stability. In this study, a benzothiadiazole-based nonbranching functionalized covalent organic framework (COF) material (TPS-COF) by one-step synthesis was reported, which exhibited a high specific surface area of 1564 m2 g-1, high crystallinity and stability attributed to its high conjugated linkage structure of benzothiadiazole. In addition, due to the rich S and N elements of the benzothiadiazole unit, it exhibited excellent adsorption performance on Hg2+, including excellent adsorption amount (1040 mg g-1), high initial adsorption rate (448 mg g-1 min-1) and very short adsorption equilibrium time (10 min), with an efficient removal rate of Hg2+ in the pH range of 2-8. After desorption, the TPS-COF still retained good pore stability, adsorption capacity, and reusability. Such a one-step synthetic unbranched functionalization strategy provides further insights to achieve a good balance between the high crystallinity, functionality and stability of COFs.