Thiophene-Based Covalent Organic Frameworks: Synthesis, Photophysics and Light-Driven Applications

Covalent organic frameworks-based materials for antibiotics fluorescence detection

Antibiotics play a vital role in safeguarding people's health since most bacterial infection can be efficiently controlled and cured by treating with suitable antibiotics. However, excessive use of antibiotics in husbandry and aquaculture leaded to the pollution of eco-environment. Thus, it is important to develop simple facile methods and effective functional materials for quick on-site analysis of antibiotics. Covalent organic frameworks (COFs), as a kind of porous crystalline covalent bond linked polymers, have demonstrated its power in multiple fields. Herein, we will discuss COFs-based materials utilized as antibiotics sensors with fluorescence method. For each sensor, we will mainly discuss the mechanism for antibiotics recognition, the preparation, characterization and fluorescence sensing performance of specific antibiotics. The mechanism to illustrate the interaction between sensors and antibiotics analytes would also be stressed.

Covalent Organic Frameworks Based Electrocatalysts for Two-Electron Oxygen Reduction Reaction: Design Principles, Recent Advances, and Perspective

Hydrogen peroxide (H2O2) is an environmentally friendly oxidant with a wide range of applications, and the two-electron pathway (2e-) of the oxygen reduction reaction (ORR) for H2O2 production has attracted much attention due to its eco-friendly nature and operational simplicity in contrast to the conventional anthraquinone process. The challenge is to design electrocatalysts with high activity and selectivity and to understand their structure-activity relationship and catalytic mechanism in the ORR process. Covalent organic frameworks (COFs) provide an efficient template for the construction of highly efficient electrocatalysts due to their designable structure, excellent stability, and controllable porosity. This review firstly outlines the design principles of COFs, including the selection of metallic and nonmetallic active sites, the modulation of the electronic structure of the active sites, and the dimensionality modulation of the COFs, to provide guidance for improving the production performance of H2O2. Subsequently, representative results are summarized in terms of both metallic and metal-free sites to follow the latest progress. Moreover, the challenges and perspectives of 2e- ORR electrocatalysts based on COFs are discussed.

Spin-Steered Photosynthesis of H2O2 in Magnetic Single-Atom Modified Covalent Triazine Frameworks: A Density Functional Theory Study

Covalent Organic Frameworks (COFs) demonstrate promising potential in the photocatalytic synthesis of H2O2 owing to favorable light absorption, superior charge separation, and considerable surface area. However, the efficiency of H2O2 photosynthesis is impeded by insufficient O2 adsorption sites and a high reaction barrier. In this work, various metal single atoms (Fe, Co, Ni) are introduced onto covalent triazine frameworks (CTFs) with N-N coordination sites to significantly enhance O2 adsorption and optimize H2O2 synthesis. Computational findings suggest that the presence of Fe, Co, and Ni not only enhances O2 adsorption but also exerts an influence on the reaction pathway of H2O2. Significantly, Fe exhibits a distinct advantage in modulating O2 adsorption through its unique electron spin state when compared to Co and Ni, as confirmed by crystal orbital Hamilton population (COHP) analysis. Additionally, this integration of metal atoms also improves light absorption and charge separation in CTFs. The study provides strategic insight into elevating H2O2 production by incorporating tailored metal single atoms into COFs.

Thiophene-Based Covalent Triazine Frameworks as Visible-Light-Driven Heterogeneous Photocatalysts for the Oxidative Coupling of Amines

This study reports on a metal-free Covalent Triazine Framework (CTF) incorporating bithiophene structural units (TP-CTF) with a semicrystalline structure as an efficient heterogeneous photocatalyst under visible light irradiation. The physico-chemical properties and composition of this material was confirmed via different characterization solid-state techniques, such as XRD, TGA, CO2 adsorption and FT-IR, NMR and UV-Vis spectroscopies. The compound was synthesized through a solvothermal process and was explored as a heterogeneous photocatalyst for the oxidative coupling of amines to imines under visible light irradiation. TP-CTF demonstrated outstanding photocatalytic activity, with high conversion rates and selectivity. Importantly, the material exhibited exceptional stability and recyclability, making it a strong candidate for sustainable and efficient imine synthesis. The low bandgap of TP-CTF enabled the efficient absorption of visible light, which is a notable advantage for visible-light-driven photocatalysis.

Effect of Controlling Thiophene Rings on D-A Polymer Photocatalysts Accessed via Direct Arylation for Hydrogen Production

Conjugated polymer photocatalysts for hydrogen production have the advantages of an adjustable structure, strong response in the visible light region, adjustable energy levels, and easy functionalization. Using an atom- and step-economic direct C-H arylation method, dibromocyanostilbene was polymerized with thiophene, dithiophene, terthiophene, and fused thienothiophene and dithienothiophene, respectively, to produce donor-acceptor (D-A)-type linear conjugated polymers containing different thiophene derivatives with different conjugation lengths. Among them, the D-A polymer photocatalyst constructed from dithienothiophene could significantly broaden the spectral response, with a hydrogen evolution rate up to 12.15 mmol h-1 g-1. The results showed that the increase in the number of fused rings on thiophene building blocks was beneficial to the photocatalytic hydrogen production of cyanostyrylphene-based linear polymers. For the unfused dithiophene and terthiophene, the increase in the number of thiophene rings enabled more rotation freedom between the thiophene rings and reduced the intrinsic charge mobility, resulting in lower hydrogen production performance accordingly. This study provides a suitable process for the design of electron donors for D-A polymer photocatalysts.

Tunable Donor-Acceptor Linear Conjugated Polymers Involving Cyanostyrylthiophene Linkages for Visible-Light-Driven Hydrogen Production

In this paper, an atom- and step-economic direct C-H arylation polymerization (DArP) strategy was developed to access cyanostyrylthiophene (CST)-based donor-acceptor (D-A) conjugated polymers (CPs) used for photocatalytic hydrogen production (PHP) from water reduction. The new CST-based CPs CP1-CP5 with varied building blocks were systematically studied by X-ray single-crystal analysis, FTIR, scanning electron microscopy, UV-vis, photoluminescence, transient photocurrent response, cyclic voltammetry measurements, and a PHP test, which showed that the phenyl-cyanostyrylthiophene-based CP3 exhibits a superior hydrogen evolution rate (7.60 mmol h^-1 g^-1) compared to other conjugated polymers. The structure-property-performance correlation results obtained in this study will provide an important guideline for the rational design of high-performance D-A CPs for PHP applications.

Thiophenes-Naturally Occurring Plant Metabolites: Biological Activities and In Silico Evaluation of Their Potential as Cathepsin D Inhibitors

Naturally, thiophenes represent a small family of natural metabolites featured by one to five thiophene rings. Numerous plant species belonging to the family Asteraceae commonly produce thiophenes. These metabolites possessed remarkable bioactivities, including antimicrobial, antiviral, anti-inflammatory, larvicidal, antioxidant, insecticidal, cytotoxic, and nematicidal properties. The current review provides an update over the past seven years for the reported natural thiophene derivatives, including their sources, biosynthesis, spectral data, and bioactivities since the last review published in 2015. Additionally, with the help of the SuperPred webserver, an AI (artificial intelligence) tool, the potential drug target for the compounds was predicted. In silico studies were conducted for Cathepsin D with thiophene derivatives, including ADMET (drug absorption/distribution/metabolism/excretion/and toxicity) properties prediction, molecular docking for the binding interaction, and molecular dynamics to evaluate the ligand-target interaction stability under simulated physiological conditions.