Highly Efficient Silver Catalyst Supported by a Spherical Covalent Organic Framework for the Continuous Reduction of 4-Nitrophenol.

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.