Magnetically Driven Self-stirring Micro Catalysts Prepared By Pneumatic Extrusion Printing

Based on the needs of experiments and production in the fields of chemistry,chemical industry and biopharmaceuticals,commercial magnetic stirring bars are widely used to drive rotating blades in chemical reactions.However,there are some application limitations of magnetic stirrers.For example,such macroscopic approaches of centimetre size are applicable for the laboratory-level reaction system of the g/kg level,but impractical for ultra-small systems such as micro-droplet and chip-level micro-system reactions.Moreover,some heterogeneous catalysts with the poor mechanical stability are prone to be destroyed by external stirring.Compared with the traditional magnetic stirrers,the nano-stirrers not only overcome some problems such as difficulty in being applicable to micro-reaction systems,but also exhibit outstanding nano-catalysis performance.However,the series of new questions,such as the complicated preparation,uncontrollable morphology and poor reproduction of the nano-scale,make the difficulty of preparing nano-sized stirrers in large quantities,limiting their large-scale industrial applications.Herein,inspired by pneumatic extrusion printing technology and metal-organic frameworks,we propose a new kind of micro-catalyst（Fe₃O₄/X MC）with magnetically-actuated stirring function,which is accomplished by pneumatic printing technology.This kind of catalyst has been successfully used in heterogeneous catalysis and their catalytic performance has been studied and summarized in detail.The first part:in this work,the MCs with catalytic activity and self-stirring performance were designed and synthesized.By adjusting the printing parameters and magnetic field intensity,the spindle MCs based on metal organic framework（MOFs）with certain aspect ratio and size can be obtained.The printing speed can reach 18,000micro catalysts per hour with one nozzle,which could realize the mass production of laboratory and even industrial-grade miniature self-stirring catalysts.In addition,the experiment proves that the printing strategy can be widely applied to a variety of heterogeneous catalysts other than MOF,such as mesoporous SiO₂,zeolite,metal oxide and so on.The second part:After successful design and synthesis of Fe₃O₄/X MCs,taking Fe₃O₄/ZIF-8/Pd MCs as an example,the MCs can not only act as both a catalyst and a magnetic stirrer,but also driving the molecular level stirring in the applied magnetic field,thus improving the catalytic activity.The MCs maintains good stability and performs well in a variety of applications for the reason that they are not limited by external stirring.In order to prove the superiority of the catalyst’s catalytic performance,Fe₃O₄/ZIF-8/Pd MC and Fe₃O₄/MIL-101/Au MC were applied in the degradation experiment of micro-droplet to test the self-stirring catalytic performance of the catalysts in the micro-reaction system.In order to solve the problem of rapid mass transfer in the photocatalytic microreactor,Fe₃O₄/ZnO MC with photocatalytic ability was synthesized and applied to a high-throughput photocatalytic microreactor.The performance and stability of self-stirring and external stirring of Fe₃O₄/ZIF-8/Pd MC and Fe₃O₄/SiO₂/Pd MC were compared in liquid phase hydrogenation reaction.These results showed that Fe₃O₄/ZIF-8/Pd MC and Fe₃O₄/MIL-101/Au MC exhibited brilliant self-stirring catalytic performance and microsystem application,Fe₃O₄/ZnO MC showed excellent photocatalytic degradation performance,and Fe₃O₄/ZIF-8/Pd MC exhibited better stability than ZIF-8/Pd powder under external stirring.