Recent advances in adsorptive removal and photocatalytic reduction of Cr(VI) by porous organic polymers (POPs)

Chromium plays important roles in many industrial processes, and hexavalent chromium (Cr(VI)) has become a major pollutant of global concern. Great efforts have been taken for Cr(VI) detoxification. Among the many technologies, adsorptive removal and photocatalysis stand out owing to the merits of high efficiency, simplicity, and low cost. Porous organic polymers (POPs), which contain permanent and tunable porosity, high specific surface area, abundant structural adjustability, and excellent stability, can be excellent materials for adsorption and photocatalysis. The structural diversity of building units and the wide compatibility with other materials make POPs suitable for precisely regulating the structure–activity relationship of POPs for Cr(VI) removal. This article provides an overview of recent advancements in the utilization of POPs for adsorptive removal and photocatalytic reduction of Cr(VI). Firstly, we introduce diverse synthetic strategies for POP-based materials bearing different functional groups, including bottom-up synthesis, post-synthetic modification, and in-situ polymerization technology. Secondly, we delve into the comprehensive discussion of various POP-based materials specifically designed for adsorptive Cr(VI) removal, with a focus on nitrogen-rich POPs such as diverse ionic POPs. Thirdly, we present novel POP-based materials essential for the photocatalytic reduction of Cr(VI), including donor–acceptor POPs and hybrid heterojunctions. Finally, we conclude by discussing the future prospects and potential developments in this field.