Pore Space Partition Synthetic Strategy in Imine-linked Multivariate Covalent Organic Frameworks

Abstract

Partitioning the pores of covalent organic frameworks (COFs) is an attractive strategy for introducing microporosity and achieving new functionality, but it is technically challenging to achieve. Herein, we report a simple strategy for partitioning the micropores/mesopores of multivariate COFs. Our approach relies on the predesign and synthesis of multicomponent COFs through imine condensation reactions with aldehyde groups anchored in the COF pores, followed by inserting additional symmetric building blocks (with C 2 or C 3 symmetries) as pore partition agents. This approach allowed tetragonal or hexagonal pores to be partitioned into two or three smaller micropores, respectively. The synthesized library of pore-partitioned COFs was then applied for the capture of iodine pollutants (i.e., I 2 and CH 3 I). This rich inventory allowed deep exploration of the relationships between the COF adsorbent composition, pore architecture, and adsorption capacity for I 2 and CH 3 I capture under wide-ranging conditions. Notably, one of our developed pore-partitioned COFs (COF 3-2P) exhibited greatly enhanced dynamic I 2 and CH 3 I adsorption performances compared to its parent COF (COF 3) in breakthrough tests, setting a new benchmark for COF-based adsorbents. Results present an effective design strategy toward functional COFs with tunable pore environments, functions, and properties.

Reversible Amine-to-Imine Chemistry at a Covalent Organic Framework for Sustainable Uranium Redox Separation

“…Multiple stable oxidation states under ambient conditions at COFs have been achieved previously using chemical transformations and postsynthetic modification (PSM). PSM techniques have been developed as an alternative to increase the structural diversity of COFs while avoiding the complex synthesis of new precursors or linkers. , For uranium absorption, PSM has been used to install amidoxime linkers for uranyl ion absorption, modulation of COF pore size and selectivity, and for tuning charge distribution. − For instance, the imine-linked COF formed from the solvothermal reaction of 1,3,5-triformyl benzene (TFB) and 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)­trianiline (TTA), PI-3, can undergo linkage conversions to amide, nitrone, or amine bonds from the starting imine linker. Changes at this carbon–nitrogen bond linker, in particular the reduction to the amine-linked COF, represent multiple stable oxidation state changes, which may be exploited here for sustainable URS and material recovery.…”

Pore Regulation of Carboxyl-Functionalized Hyper-Crosslinked Polymers and Their Efficient Aniline Adsorption

“…They are employed to remove crystal violet (CV, cationic) and alizarin red (ARS, anionic) dyes in water. Xu et al creatively partitioned the mesopores of the two-dimensional covalent organic frameworks (COFs) from mesoporous 2.9 nm to microporous 6.5 Å. Hao et al first synthesized the aldehyde-anchored COFs and then inserted some additional building blocks as the pore partition agents. As a result, the tetragonal or hexagonal pores of the original COFs were partitioned into smaller micropores, increasing the dynamic adsorption of I 2 and CH 3 I.…”

Two-Dimensional Covalent Organic Frameworks with Pentagonal Pores

“…Covalent organic frameworks (COFs) have emerged as a new kind of porous polymers, which allow the assembly of various organic building blocks through strong covalent bonds at atomic precision. − Owing to their specific construction modes, most COFs have exhibited multiple advantages, such as high crystallinity, flexible structures, and strong robustness, which endow these materials with tremendous application foreground in gas adsorption, − heterogeneous catalysis, − optoelectronics, − sensing, − and energy storage. − Although a large number of two-dimensional (2D) COFs with triangular, tetragonal, and hexagonal pores have been developed through the rational combination of building blocks with different symmetries, − the construction of COFs with pentagonal pores remains a great challenge as it conflicts with the principle of plane geometry. − …”