A new core−shell nanocomposite was designed by functionalization of a Co 3 O 4 quantum dots (Co 3 O 4 -QDs) core with terephthalic acid (TPA) and growth of an Fe-infinite coordination polymer (Fe-ICP) shell on the core surface. High-resolution transmission electron microscopy (HR-TEM) confirmed the core− shell structure of the prepared Co 3 O 4 -QDs@Fe-ICP nanocomposite. Co 3 O 4 -QDs@ Fe-ICP exhibited high catalytic, visible light photocatalytic, and photoelectrocatalytic activity in degradation of rhodamine B (RhB), reactive orange 29 (RAO29), and crystal violet (CV) as compared to the individual Co 3 O 4 -QDs and Fe-ICP. The high photocatalytic, photoelectrocatalytic, and catalytic activities of Co 3 O 4 -QDs@ Fe-ICP in comparison with Co 3 O 4 -QDs and Fe-ICP were attributed to the interconnection of Co 3 O 4 -QDs and Fe-ICP within the core−shell structure. Impressively, the existence of the Fe-ICP shell is critical for not only efficient charge separation and enhancing the catalytic performance but also preventing Co 3 O 4 -QDs from aggregation during the degradation process.