A multi-dye@MOF composite boosts highly efficient photodegradation of an ultra-stubborn dye reactive blue 21 under visible-light irradiation

Reactive blue 21 (RB21), a phthalocyanine dye, is frequently used in the textile industry and has been rarely researched for decontamination in wastewater. Moreover, no existing approach exhibits effective removal capability. It is therefore highly imperative to quest for alternative solution to address this problem. MOFs have recently appeared as new functional materials for environmental remediation due to their intrinsic features of high porosities and light response. Although a few MOFs are inherently responsive to visible light, most MOF materials can mainly harvest UV light; this dramatically limits the utilization of solar energy. Inspired by our previous results that the dye@MOF composite could effectively photodegrade organic dyes under visible-light irradiation, in the current study, three yellow/red/blue cationic dyes were successfully assembled into an identical MOF host singly, dually, and triply; this led to the formation of seven new multi-dye@MOF composites. Systematic investigations reveal that the seven composites can comparatively photodegrade RB21 under visible-light irradiation. Among them, the composite triple-dye@MOF displays the most efficient performance of 95.36%, which is far superior to that of the commercial P25. This finding may open up a new avenue to construct novel composites towards addressing some unresolved environmental issues, i.e. the decontamination of ultra-stubborn dyes in an aqueous solution.