Boosting and tuning the visible photocatalytic degradation performances towards reactive blue 21 via dyes@MOF composites

Highlights: • Composites BY24@1, BR14@1 and MB@1 with rather low Eg values of 2.19, 2.10 and 1.76 eV were prepared. • Enhanced and tunable visible photodegradation capacities towards ultra-stubborn RB 21 were presented. • The tailoring of Cu-MOF of 1 in photocatalytic degradation performances towards RB 21 has been realized. • Possible photocatalytic mechanisms including enhancing and tuning mechanisms were investigated in detail. -- Abstract: A porous copper-based metal-organic framework (Cu-MOF) of 1 was selected and further elaborately tailored by encapsulating visible-light photosensitive Basic Yellow 24 (BY24), Basic Red 14 (BR14) and Methylene Blue (MB) to generate three novel Cu-MOF-based composites BY24@1, BR14@1 and MB@1. Due to naturally inheriting the excellent photoresponsive talents from introduced dye molecules, the visible-light absorption performances of three composites have been markedly improved and their energy band gaps (Eg) were determined to be 2.19, 2.10 and 1.76 eV, respectively. Further investigations demonstrated that three composites could effectively photodegrade Reactive Blue 21 (RB21) under visible light irradiation, with degradation efficiencies increased from 78.8% of 1 to 89.0% for BY24@1, 91.5% for BR14@1 and 97.3% for MB@1. The high-efficiency and diversified performances of dye@1 in destroying RB21 reveal the significant achievements in tailoring the photocatalytic capabilities via introducing dyes with different photosensitivity into identical porous copper-organic framework. This elaborate sensitization strategy may open up more applications of such composites sensitized by high visible photosensitive dyes. In addition, photocatalytic recyclability and optimum pH conditions of MB@1, the COD_Cr values of original/residual RB21 solution, possible photocatalytic mechanisms including enhancing and tuning mechanisms also were investigated in detail.