A luminescent one-dimensional covalent organic framework for organic arsenic sensing in water

Roxarsone(ROX)is a commonly used antibacterial and growth-promoting additive to animal feed.The development of an effective method for detecting ROX and its conversion products is of importance because of their potential harm to human health and ecosystem.Herein,we report the designed synthesis of a novel one-dimensional covalent organic framework(1D COF),named EP-COF,and its application as a fluorescent probe for ROX sensing.EP-COF is constructed based on imine linkages,exhibiting high crystallinity,strong fluorescence emission,and good dispersibility in water.It displays a remarkable capability to efficiently detect ROX,with an impressive detection limit of 4.5 nmol/L.Moreover,EP-COF also offers advantages of excellent selectivity,and high structural stability.This work not only presents a promising approach for the detection of harmful substances like ROX,but also serves as a valuable reference for exploring application of 1D COFs in chemical sensing.

Converting Azine Linkage into Highly Stable(Thio)Urea-Based Bicyclic-Fused-Ring Connections in Covalent Organic Frameworks via Criss-Cross[3+2]Cycloaddition

Exploring new linkage chemistry is of fundamental significance for covalent organic frameworks(COFs)to expand their structure and functional diversity.Herein,we report a strategy for converting azine linkage into urea-and thiourea-based fused-ring connections in COFs by criss-cross[3+2]dipolar cycloaddition of azine with HNCO or KSCN.The as-prepared COFs with cyclized linkages exhibited enhanced chemical and thermal stability by locking the dynamic C=N linkages in the progenitor.Moreover,functions could be introduced into the skeleton of COFs by this postsynthetic cyclization method,which enabled significant improvements in functionality,demonstrated by the studies on CO_(2)/N_(2) selective sorption,proton conduction,and Hg^(2+)adsorption.The use of this[3+2]cycloaddition strategy not only enriched the chemistry of linkage conversion for COFs but also offered a new way to fabricate fused-ring-linked COFs,thereby representing a high level of controllability on connectivity and functionality of COFs.

A heteropore covalent organic framework for adsorptive removal of Cd(Ⅱ) from aqueous solutions with high efficiency

A heteropore covalent organic framework(COF) integrating tetraphenylethene skeleton and catechol segment is designed and synthesized.It exhibits extremely high stability in water under different pH conditions,which makes it an excellent material for adsorptive removal of Cd(Ⅱ) from aqueous solutions with very fast adsorption kinetics,high uptake capacity,and good recyclability.

Designed Synthesis of a Two-Dimensional Covalent Organic Framework with Three-Level Hierarchical Porosity

of main observation and conclusion Covalent organic frameworks(COFs)with hierarchical porosity have drawn considerable attention very recently due to their advantages over the COFs with uniform porosity in some aspects.However,the design strategies for the construction of this type of COFs,namely heteropore COFs,are quite limited.We herein report a facile approach to constructing a two-dimensional COF which possesses three different kinds of pores.Its structure is confirmed by powder X-ray diffraction and nitrogen sorption studies.The successful construction of the triple-pore COF represents a new method to access COFs with high hierarchical porosity.

A two-step solvothermal procedure to improve crystallinity of covalent organic frameworks and achieve scale-up preparation

Covalent organic frameworks(COFs),as a novel class of functional polymers,exhibit versatile applica-tions due to their crystalline porous structures and conjugated skeletons.However,synthesis of COFs with high crystallinity still faces great challenges,especially for scale-up preparation.Herein we report a two-step solvothermal process to improve crystallinity of COFs.The first step focuses on polycondensa-tion of monomers with no need for optimizing crystallization conditions.In the second step,appropriate solvothermal conditions are used to facilitate crystallization of the COFs through defects correction and structural repairing.Furthermore,this strategy could also be applicable to scale-up synthesis of high qual-ity COFs,which lays a foundation for their practical applications.

A Study on Constitutional Isomerism in Covalent Organic Frameworks:Controllable Synthesis,Transformation,and Distinct Difference in Properties

Isomerism is an essential and widespread phenomenon in organic chemistry but rarely observed in covalent organic frameworks(COFs),a novel class of crystalline porous organic polymers with versatile applications.Herein,we give an account of the first example of a controllable synthesis of constitutional isomers of a COF.The two isomers exhibited marked differences in their gas/vapor adsorption behaviors and chemical stability in various solvents.Furthermore,structure transformation from one isomer to the other was realized.This work not only paves the way for rational design and synthesis of COF isomers but also provides a vivid example of structure–property relationship in crystalline porous polymers.

Effects of connecting sequences of building blocks on reticular synthesis of covalent organic frameworks

The principle of reticular chemistry has been widely used to guide the design of crystalline porous materials such as metal organic frameworks(MOFs)and covalent organic frameworks(COFs).While in the early strategies only the symmetries of the building blocks were considered for reticular synthesis of COFs,recently a few researches on COFs with hierarchical porosities indicate that connecting sequence of building blocks also plays a crucial role in determining crystalline structures of COFs.However,this important phenomenon has not been systematically investigated yet.In this article,a model system has been established to demonstrate how different connecting sequences of two C_(2v)-symmetric building blocks lead to the formation of four two-dimensional(2D)COFs with distinct framework structures.To verify this concept,target synthesis was conducted to produce three COFs,whose structures were confirmed by powder X-ray diffraction and pore size distribution analysis.

A supramolecular bottlebrush polymer assembled on the basis of cucurbit[8]uril-encapsulation-enhanced donor-acceptor interaction

A supramolecular bottlebrush polymer has been constructed in water through the self-assembly of a rigid electron-deficient building block and an electron-rich monomer which bears two tetraethylene glycol chains,driven by CB[8]-encapsulation-enhanced donor-acceptor interaction.The as-formed supramolecular bottlebrush polymer has been characterized by -1H NMR titration experiment,UV-vis spectroscopy,DLS and 2D -1H NMR DOSY.

A self-assembled framework that interpenetrates in crystal but does not interpenetrate in solution

A porous supramolecular framework has been for the first time revealed to undergo interpenetration in crystal and noninterpenetration in solution.A new supramolecular organic framework Bu-SOF has been constructed from the co-assembly of a tetracationic tetrahedral monomer and cucurbit[8]uril(CB[8])in water through the encapsulation of two anti-parallel n-butyl chains by CB[8].X-ray diffraction analysis reveals that Bu-SOF forms 3-fold interpenetrated networks in crystals grown by evaporation of its solution in water.1 H NMR,dynamic light scattering and isothermal titration calorimetric experiments confirm that Bu-SOF is also formed in water.Solid samples,prepared by lyophilizing the aqueous solution of Bu-SOF,can adsorb nanoscaled organic dyes,supporting the porosity of the framework and thus non-interpenetration in solution.The avoidance of interpenetration of Bu-SOF in solution has been attributed to the filling of water inside the porous framework as well as the electrostatic repulsion of the appended bipyridinium units of the tetrahedral building block.

Toward a Two-Dimensional Supramolecular Organic Framework with High Degree of Internal Order via Amphiphilic Modification

Solution-phase self-assembly of two-dimensional(2D)networks with a high degree of internal order and long-range periodicity is a great challenge.Herein,we report a rational design to improve 2D self-assembly in water through amphiphilic modification of the building block.An amphiphilic tritopic molecule(1)is designed and synthesized by introducing three hydrophilic oligo(ethylene glycol)moieties and three hydrophobic hexyl chains.The assembly of 1 and cucurbit[8]uril(CB[8])leads to the formation of a Janus 2D supramolecular organic framework(SOF),which further creates unique bilayer supramolecular networks and exhibits an unprecedentedly high degree of internal order and long-range periodicity.In contrast,the assembly of a nonamphiphilic analog(2)with CB[8]only generates a 2D SOF with a lower degree of internal order,suggesting that the inherent amphiphilicity of 1 plays a crucial role in improving its 2D self-assembly in aqueous phase.