Yan Jiaqi,Fu Weiwen,You Kuiyi,Zhao Fangfang,Luo He’an
A solvent-free, acid-free, and efficient strategy was developed for the selective preparation of 4-nitro-o-xylene (4-NOX) from the catalytic nitration of o-xylene with NO 2 mediated O 2 over BiCl 3 immobilized silicic acid catalyst (BiCl 3 -SA). The results indicated that the Lewis acid BiCl 3 -SA conjoined NO 2 –O 2 as a composite system synergistically promotes o-xylene conversion and 4-NOX selectivity. Under optimal conditions, 52.4% of o-xylene conversion with 68.4% 4-NOX selectivity was obtained at 35 °C. The characterization demonstrated that the highly dispersed metal Bi species form stable chemical bonds with the SA surface, which can effectively inhibit the loss of metal species and generate abundant acid sites. The developed catalyst is not only inexpensive but also has excellent stability and catalytic performance. Furthermore, a plausible mechanism for the catalytic nitration of o-xylene using NO 2 as a nitration agent over BiCl 3 -SA was proposed. This work provides an eco-friendly and practical protocol for improving desirable 4-NOX selectivity and reducing the discharge of acidic wastewater, with potential application prospects. Graphical abstract
Nitrogen dioxide (NO2), the main component of pollutants in atmospheric environments, causes and exacerbates respiratory diseases, especially during outdoor sports even at the 100 ppb level. Currently, environmental gas detection still faces challenges such as high detection limits, low SNR, and low sensitivity. A NO2 sensor based on In(OH)3-α-Fe2O3–ZnO was prepared using a hydrothermal method, featuring an ultralow detection limit of 82 ppt, an exceptionally high SNR of 574,000, and an ultrahigh sensitivity of 252.25 mV/ppm (100 ppb to 1 ppm). And this sensor exhibits excellent response, selectivity, and repeatability. These excellent sensing characteristics come from the adsorbed oxygen on the surface of the material with the formation of n–n heterojunctions. Additionally, a low-power, portable, and cost-effective environmental monitoring system (named Smart Breath Sentinel (SBS)) was designed to intelligently upgrade ordinary masks. SBS enables real-time wireless environmental gas monitoring with integrated humidity compensation to ensure accurate measurements in high-humidity environments. SBS has already been tested in multiple environments, and the test results have proven the feasibility of SBS. This sensor based on In(OH)3-α-Fe2O3–ZnO demonstrates significant potential for applications aimed at enhancing human safety.
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