Recent Advances in Metal–Organic Framework (MOF) Composites for Contaminant Adsorption, Photocatalytic Degradation, and Drug Delivery Applications

The increasing discharge of pharmaceuticals, dyes, and toxic ions has intensified the need for efficient adsorption and degradation technologies. Metal–organic frameworks (MOFs) have attracted considerable attention for environmental remediation, owing to their well-defined porous structures, exceptionally high specific surface areas, abundant accessible active sites, tunable pore architectures, and structural diversity. However, the practical application of pristine MOFs is often hindered by several limitations, including inadequate stability in aqueous environments and limited mass-transfer efficiency. These drawbacks can significantly restrict the large-scale and industrial utilization of MOF materials. The integration of MOFs with functional materials such as carbonaceous substrates, polymers, metals/metal oxides, porous silica, magnetic nanoparticles, COFs, MOFs, POMs, graphitic carbon nitride, MXenes, and enzymes enhances their stability, hydrophobicity, dispersibility, electron-transfer capability, mechanical strength, and reusability. These synergistic effects enable MOF composites to achieve remarkable performance in the removal of a wide range of contaminants through adsorption and catalytic degradation processes. This review provides a systematic overview of recent progress in MOF-based composites for the removal of dyes, pharmaceutical contaminants, and metal ions, as well as their applications in drug delivery. A particular emphasis is placed on composite design strategies, structure–performance relationships, and the synergistic mechanisms responsible for the enhanced functionality of different composite systems.