Multi‐Core–shell TiO 2 NPs@ZIF‐8 Composite for Enhanced Photocatalytic Degradation and Adsorption of Methylene Blue and Rhodamine‐B

Multi‐Core–shell TiO 2 NPs@ZIF‐8 composites were synthesized by in situ encapsulation of different amounts of TiO 2 NPs (150, 300 and 500 μL suspension of TiO 2 NPs in methanol) in ZIF‐8 at room temperature. Encapsulation of TiO 2 NPs in ZIF‐8 was confirmed by transmission electron microscopy and X‐ray photoelectron spectroscopy. ZIF‐8 and its core–shell composites have similar crystal structure and morphology as confirmed by powder X‐ray diffraction analysis and scanning electron microscopy. The detailed photocatalytic degradation and adsorption studies of methylene blue and rhodamine‐B were investigated by considering various factors, viz. amount of loading of TiO 2 NPs in ZIF‐8, amount of photocatalyst, pH and initial concentration of the dye. At higher pH (11.5−12.6), TiO 2 NPs@ZIF‐8 composite exhibited higher (≈ 8 times) photocatalytic activity as compared to TiO 2 NPs and the optimum amount of TiO 2 NPs@ZIF‐8 composite was 10 mg for the maximum photodegradation of 3.19 mg L −1 (93 %) and 2.4 mg L −1 (57 %) of methylene blue and rhodamine‐B, respectively.