A sensing platform for ascorbic acid based on the spatial confinement of covalent organic frameworks.

Essential to many activities in our bodies, ascorbic acid is a small molecule essential to human health and physiological processes. In this study, a covalent organic framework called TpNda-COF was synthesized, which is composed of Tp (triformylephloroglucinol) and Nda (1, 5-napthalenediamine). This framework acts as a mimic enzyme and displays excellent oxidase-like activity when stimulated with purple light (at = 405 nm). It catalyzes the oxidation of 3,3',5,5'-tetramethylbenzydine (TMB) by generating O2- free radicals in the presence of oxygen. The resulting oxTMB shows a characteristic absorption peak at 652 nm. The biomimetic catalysis efficiency is significantly improved due to spatial restriction. By introducing ascorbic acid (AA) in the system, the blue oxTMB is reduced to colorless TMB. The decrease in absorption peak intensity can be quantitatively measured using a UV-Vis spectrophotometer, enabling the detection of AA. The sensing platform demonstrates excellent selectivity and sensitivity. It has a wide linear detection range from 5 µM to 50 µM, with a low detection limit of 1.44 µM. Advantages such as the easy control of light, high stability and efficient oxidation are provided by the TpNda-COF mimic oxidase. This innovative method presents a promising and cost-effective approach for rapid detection of ascorbic acid, with potential applications across various fields.

Ni3V2O8 nanoflower mimetic enzyme constructs a dual-signal system for ascorbic acid detection.

Ascorbic acid is a nutritional small molecule essential to human life activities and health, playing a vital role in many physiological processes. Fresh fruits and beverages can provide abundant AA to maintain human metabolic balance. Therefore, it is of great significance to develop a nanomaterial with superior nanozyme activity for rapid and convenient detection of ascorbic acid (AA) in fruits and beverages. Herein, a dual-signal sensing platform based on UV-vis absorption and test strip chromaticity for the quantitative determination of AA is presented. The sensing platform is based on the horseradish peroxidase-like activity of Ni3V2O8 nanoflowers, which catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by hydrogen peroxide to the blue oxide TMB (ox TMB). The ox TMB produced by the oxidation has a characteristic absorption peak at 650 nm. In the presence of AA, the blue ox TMB is reduced to colorless TMB, and the quantitative detection of AA can be achieved by detecting the decrease in intensity of the absorption peak by UV-Vis spectrophotometry. Under the optimal experimental conditions, the sensing platform exhibited excellent sensitivity and selectivity. A wide linear range of 0.1 µM to 40 µM with a detection limit of 0.032 µM was obtained. The linear equation is ΔA = 0.02513c + 0.1164 with a correlation coefficient of 0.9979. It showed excellent properties in the detection of real samples of fruit juices and beverages, meanwhile, a method for the rapid detection of AA based on chromaticity change of test strips was constructed with high sensitivity and convenience. The linearity range for the ascorbic acid was 1-50 µM with LOD of 0.42 µM. The developed sensing platform has the capability to quickly and accurately detect ascorbic acid (AA) in fresh fruits and beverages. This proposed method offers a new and promising approach for the rapid and cost-effective detection of ascorbic acid, which has a wide range of potential applications.

Porphyrinic Porous Aromatic Frameworks for Carbon Dioxide Adsorption and Separation.

The capture of carbon dioxide (CO2 ) from industrial process emissions is increasingly important for the mitigation and prevention of the disruptive effects of global warming. In this study, PAF (porous aromatic frameworks)-TPB(1,3,5-triphenylbenzene) and three-dimensional PAF-TPM (tetraphenylmethane) porphyrin-based aromatic porous materials were synthesized through the Scholl reaction. The CO2 and N2 adsorption isotherms at 273 K and 298 K were studied to determine the performance in carbon dioxide capture at flue gas conditions. There is a significant difference in the adsorption capacity of the two materials for CO2 and N2 , so they can be used for CO2 /N2 adsorption separation. PAF-TPM has better CO2 /N2 separation at low pressure (150 mbar), while PAF-TPB has the advantage of greater CO2 /N2 separation at high pressure (1 bar). It can be applied to CO2 adsorption separation at low and high pressure, respectively. In particular, PAF-TPB has a CO2 /N2 separation efficiency of up to 100.9 at 1 bar and 273 K. This work provides ideas for the design and synthesis of organic porous materials for the adsorption separation of CO2 and N2 .