Towards application of a covalent organic framework-silver nanoparticles@sand heterostructure as a high-efficiency catalyst for flow-through reduction of organic pollutants

Highlights: • A covalent organic framework-silver nanocomposite supported by polydopamine-coated sand (COF-Ag NPs@Sand) was fabricated. • COF-Ag NPs@Sand showed an efficient catalytic activity towards organic pollutants. • COF-Ag NPs@Sand showed a good stability under the flow-through process. Noble metal nanoparticles supported by covalent organic frameworks (COFs) exhibited excellent catalytic performances towards organic pollutants, while their applications are limited by the recovery and reuse from the mixture due to their small size. Here, we solved this issue by supporting covalent organic framework-silver nanoparticles on sand and used as a catalyst for reduction of organic pollutants. Both static and flow-through experiments were carried out and good catalytic performances were exhibited. High flux (2000 L m⁻²h⁻¹)/reduction efficiency (more than 99%) towards 4-nitrophenol, Congo red, and methylene blue, were obtained under the flow-through process. Furthermore, after testing 24 h, the reduction efficiency was unaltered and only 0.34 wt% Ag ions were released from the catalyst. Besides the excellent cocatalyst of COF and the stable structure of our prepared catalyst, these good catalytic performances can be also attribute to the properties of sand which has a large size to prevent the leaching out of catalysts and a good hydrophilicity for fast passing through of wastewater. Therefore, our prepared catalyst may shed light on the application of such kinds of heterogeneous catalysts for the fast and continuous treatment of toxic and carcinogenic organic pollutants.