Critical review on magnetic separable molecularly imprinted photocatalyst: Synthesis, reaction mechanism and outlook for practical applications

Abstract

Conventional photocatalysts have been engineered over the years to achieve high photocatalytic activity with minimum input of photon energy, by narrowing their bandgap energy, improving their adsorption capacity, and enhancing the separation of photogenerated electron-hole pairs. However, conventional photocatalysts' selectivity has always been a gap, where undesired degradation of other molecules co-existing in the solution occurs, deteriorating degradation efficiency over the targeted molecules. Also, the challenge of separating these nanosized photocatalysts from the water environment decreases the process's sustainability. In response to the issues identified above, combining magnetic properties and molecular imprinting in photocatalysis technology has emerged as a promising solution. The basic idea of molecular imprinting is to prepare tailor-made materials with predefined recognition of certain molecules, where specific cavities are created on the material surface by using template molecules. The selective binding of the target pollutants to the recognition sites of molecularly imprinted photocatalysts (MIPs) allows more efficient utilization of photogenerated reactive species for degradation, providing faster degradation rates and lowering the overall energy consumption. Coupling the MIPs with magnetic properties, efficient and effective harvesting and regenerating can be achieved, providing a more sustainable option compared to conventional photocatalysts. To date, magnetic molecularly imprinted photocatalysts (MMIPs) with recognition and reusability properties have been employed in wastewater treatment, environmental remediation as well as sensor development. In this review paper, we explore the potential of MMIPs which their photodegradation mechanism, synthesis method and challenges, design criteria, applications, and future prospects are critically discussed.