Magnetic core–shell nanocatalysts: promising versatile catalysts for organic and photocatalytic reactions

ABSTRACT During the past decades, there have been enormous developments in catalysis in the form of great innovations such as precise structure characterization, surface functionalization, and effective utilization of active sites. In both academic and industrial sectors, the development of efficient nanosized catalysts has received considerable attention because it can improve the efficiency of the catalytic process and the selectivity of products, which can minimize the overall production cost and the amount of chemical wastes generated by improving the atomic efficiency. However, bulk-scale synthesis and utilization of nanocatalysts are hindered by the high synthetic cost, tedious synthesis procedure, and difficulty in the separation and recovery of the catalysts after the reactions. In this context, superparamagnetic nanoparticles have attracted much attention as a catalyst and as a support owing to their robust structure, low cost, environmental benignity, and easy separation under an external magnetic response. In this review, we focused on organic catalysis and photocatalysis using magnetically retrievable core–shell nanocatalysts with various functionalities. This review presents a comprehensive overview of the synthesis of magnetic core–shell nanocatalysts with suitable functionalities for catalysis, recent developments in organic and photocatalytic reactions using core–shell catalysts, and challenges to be addressed as part of future research activities. The first part summarizes the various synthetic methods of magnetic nanocores, and the second part overviews the detailed functionalization methods for the growth of shells on the surface of the magnetic nanocores, along with the merits and challenges to-date. In the last section, the efficiency, recoverability, and reusability of magnetic core–shell nanocatalysts are reviewed for a variety of organic and photocatalytic reactions.