Developing new materials and novel technologies for the highly efficient treatment of toxic organic pollutants is highly desirable. Chemical reduction based on heterogeneous substrate/noble metal catalysts and the reducing agent NaBH4 has become an effective method in recent years. Here, a spherical covalent organic framework (SCOF) was designed to provide basic sites for Ag ions, by which small Ag NPs were immobilized on the SCOF to form Ag NPs@SCOF microspheres. The prepared microspheres exhibited a high catalytic reduction ability toward 4-nitrophenol (4-NP). An optimized permeation flux of 2000 L m–2 h–1 (LMH) and a more than 99% 4-NP reduction efficiency were obtained with flow-through experiments, which are far better than the reported results (below 200 LMH). Moreover, the microspheres could maintain stable catalytic performance under a continuous flow-through process. Our work provides an efficient material and technology that can be applied to easily treat toxic organic pollutants.

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Background and aims Measuring specific ion fluxes from different regions of the root under practical physiological conditions is crucial for understanding metal uptake mechanisms by plants. Methods We developed and tested a neutral carrierbased liquid-membrane Pb 2+ and Cu 2+ ion selective microelectrode (ISME) to investigate ion-transport processes along the roots of three common wetland plant species. Results The Pb 2+ and Cu 2+ ISME exhibited a Nernstian response with Pb 2+ and Cu 2+ activities as low as 1.0 nM and 1.0 μM in deionized water and simulated soil solution, respectively. Phragmites australis had a region of Cu 2+ release for approximately the first 200 μm, while it exhibited Pb 2+ and Cd 2+ outward net flux up to the first 500 μm. Although in older sections of the root of Phragmites australis there were areas of influx of Cu 2+ , Pb 2+ and Cd 2+ , the overall influx was much smaller than that of Typha latifolia or Canna indica. Such a reduced uptake and/or an increased efflux of metal ions across the root-cell plasma-membrane might explain the higher resistance of Phragmites australis to metals, at least in part. Conclusions The Pb 2+ and Cu 2+ ISMEs are shown to permit detailed investigation of heavy-metal ion transport in plant roots, especially for plants used for phytoremediation.