| Summary: | Waste heat and organic contaminants are significant issues in water pollution, which has caused ecological problems and threatened human health. To provide an effective solution for wastewater recovery, we designed a novel type of multifunctional phase-change microcapsule. This type of microcapsule was synthesized using <i>n</i>-docosane as a core and a SiO<sub>2</sub>/Fe<sub>3</sub>O<sub>4</sub> composite as a base shell through in situ interfacial polycondensation with the assistance of a Fe<sub>3</sub>O<sub>4</sub> nanoparticle as a Pickering emulsion stabilizer, followed by the deposition of BiOI nanosheets on the surface of the SiO<sub>2</sub>/Fe<sub>3</sub>O<sub>4</sub> composite shell. Benefiting from the <i>n</i>-docosane core, the resultant microcapsules obtained phase-change enthalpies of 46.8–115.7 J/g for absorbing waste heat from wastewater. The deposited BiOI nanosheets promoted photocatalysis for the microcapsules to degrade organic contaminants in wastewater. Owing to the magnetic response of the Fe<sub>3</sub>O<sub>4</sub> nanoparticles, the separability and recyclability of the microcapsules were improved significantly by magnetic separation. Moreover, the microcapsules demonstrate outstanding phase-change reversibility, thermal cycling stability, and shape stability due to the tight SiO<sub>2</sub>/Fe<sub>3</sub>O<sub>4</sub> composite shell. This study provides a promising approach for designing and developing multifunctional phase-change microcapsules for waste heat recovery and wastewater treatment.
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