Covalent organic frameworks (COFs) are a class of crystalline porous organic polymers with polygonal porosity and highly ordered structures. The most prominent feature of the COFs is their excellent crystallinity and highly ordered modifiable one-dimensional pores. Since the first report of them in 2005, COFs with various structures were successfully synthesized and their applications in a wide range of fields including gas storage, pollution removal, catalysis, and optoelectronics explored. In the meantime, COFs also exhibited good performance in chemical and biological sensing, because their highly ordered modifiable pores allowed the selective adsorption of the analytes, and the interaction between the analytes and the COFs’ skeletons may lead to a detectable change in the optical or electrical properties of the COFs. In this review, we firstly demonstrate the basic principles of COFs-based chemical and biological sensing, then briefly summarize the applications of COFs in sensing some substances of practical value, including some gases, ions, organic compounds, and biomolecules. Finally, we discuss the trends and the challenges of COFs-based chemical and biological sensing.

C₃N₄/BiFeO₃heterojunction shows enhanced visible light photocatalytic efficiency.

Employing near infrared (NIR) light for photocatalytic reactions is preferable, considering effective solar utilization. Herein, the metalloid of tungsten carbide (WC) was used as an NIR-driven photocatalyst for the photodegradation of organic pollutants for the first time. The noble metal-like electronic properties of WC were proven via the analysis of its electronic occupied state using ultraviolet photoelectron spectroscopy and valence band XPS. In addition, both the experimental evidence and 3D finite element simulation revealed the NIR-responsive localized surface plasmon resonance (LSPR) behavior of the WC nanoparticles. Accordingly, the WC nanoparticles exhibited excellent UV-visible-NIR full-spectrum absorption, high NIR-triggered photocurrent response and resultant NIR-driven photocatalytic degradation performance. The NIR-mediated photocatalytic mechanism of WC was proposed based on a radical scavenging test, fluorescence observation of radical generation and spin-trapping electron paramagnetic resonance measurements. Hence, metallic WC with NIR absorption and photocatalytic activity may pave the way for the design of full-solar-spectrum-responsive photocatalysts.

Gene therapy has attracted much attention because of its unique mechanism of action, non-toxicity, and good tolerance, which can kill cancer cells without damaging healthy tissues. siRNA-based gene therapy can downregulate, enhance, or correct gene expression by introducing some nucleic acid into patient tissues. Routine treatment of hemophilia requires frequent intravenous injections of missing clotting protein. The high cost of combined therapy causes most patients to lack the best treatment resources. siRNA therapy has the potential of lasting treatment and even curing diseases. Compared with traditional surgery and chemotherapy, siRNA has fewer side effects and less damage to normal cells. The available therapies for degenerative diseases can only alleviate the symptoms of patients, while siRNA therapy drugs can upregulate gene expression, modify epigenetic changes, and stop the disease. In addition, siRNA also plays an important role in cardiovascular diseases, gastrointestinal diseases, and hepatitis B. However, free siRNA is easily degraded by nuclease and has a short half-life in the blood. Research has found that siRNA can be delivered to specific cells through appropriate vector selection and design to improve the therapeutic effect. The application of viral vectors is limited because of their high immunogenicity and low capacity, while non-viral vectors are widely used because of their low immunogenicity, low production cost, and high safety. This paper reviews the common non-viral vectors in recent years and introduces their advantages and disadvantages, as well as the latest application examples.

A WO_3−x/TiO_2−x nanotube array (NTA) heterojunction photoanode was strategically designed to improve photoelectrocatalytic (PEC) performance by establishing a synergistic vacancy-induced self-doping effect and localized surface plasmon resonance (LSPR) effect of metalloid non-stoichiometric tungsten suboxide. The WO_3−x/TiO_2−x NTA heterojunction photoanode was synthesized through a successive process of anodic oxidation to form TiO₂ nanotube arrays, magnetron sputtering to deposit metalloid WO_3−x, and post-hydrogen reduction to engender oxygen vacancy in TiO_2−x as well as crystallization. On the merits of such a synergistic effect, WO_3−x/TiO_2−x shows higher light-harvesting ability, stronger photocurrent response, and resultant improved photoelectrocatalytic performance than the contrast of WO_3−x/TiO₂, WO₃/TiO₂ and TiO₂, confirming the importance of oxygen vacancies in improving PEC performance. Theoretical calculation based on density functional theory was applied to investigate the electronic structural features of samples and reveal how the oxygen vacancy determines the optical property. The carrier density tuning mechanism and charge transfer model were considered to be associated with the synergistic effect of self-doping and metalloid LSPR effect in the WO_3−x/TiO_2−x NTA.