Towards mass production of a spherical montmorillonite@covalent organic framework@gold nanoparticles heterostructure as a high-efficiency catalyst for reduction of methylene blue

Abstract Gold nanoparticles (Au NPs) supported by a covalent organic framework (COF) exhibited a remarkably catalytic performance towards organic pollutants, while the application is limited by the recovery and reuse from the mixture due to the size of Au NPs@COF at the nanoscale. Herein, Au NPs were in situ reduced on the surface of sulfhydryl groups functionalized new COF with NaBH4, followed by the deposition on polydopamine modified micron-sized porous spherical montmorillonite (SMt) to construct a spherical SMt@COF@Au NPs heterostructure. SMt was used here due to its excellent adsorption ability towards methylene blue (MB), increasing the concentration of MB near COF@Au NPs, thus accelerating the catalytic reaction. Hence, the optimized apparent reduction rate constant (Kapp) and turnover frequency (TOF) in our experiment could reach 8.32 min−1 and 3.2 × 105 h−1, respectively, at 40 °C and pH values of 10, which is much better than the reported. Furthermore, micro-sized SMt with self-sedimentary property could be easily recovered from the mixture without any devices involved. More importantly, the granular micro-sized morphology of the SMt-based heterostructure could facile transport on the product line and reduce the fouling, facilitating mass production COF@Au NPs based catalyst for application.