Facile Synthesis of Metal-Organic Framework (ZIF-11) and Ag NPs Encapsulated-ZIF-11 Composite as an Effective Heterogeneous Catalyst for Photodegradation of Methylene Blue

Facile synthesis of metal-organic framework based on zeolitic imidazolate (ZIF-11) has been optimized to get a material withrhotopology. For the first time AgNPs in various dosing amounts (using 150, 300 and 500 mu L of its suspension in methanol) have been successfully encapsulated within ZIF-11 matrix at room temperature using binary solvent (methanol and toluene) yielding novel multi-core-shell AgNPs@ZIF-11 (AZ1, AZ2 and AZ3) composites. Encapsulation of AgNPs (particle size: 11.76 +/- 2.3 nm) has been confirmed by TEM and ultraviolet diffuse reflectance spectroscopic (UV-DRS) analysis. The lowering of band gap of ZIF-11 from 4.36 to 4.21 eV indicates the micro-environment of AgNPs within ZIF-11 framework, which has also been ensured by XPS analysis. ZIF-11 and AgNPs@ZIF-11 composites are highly stable up to 500 degrees C under air and N(2)atmosphere. It has been found that AZ1 composite exhibits excellent photocatalytic activity (almost 100% degradation) toward MB (1.6 mg/L) at pH >= 8. Further, various factors such as loading amount of AgNPs (150, 300 and 500 mu L suspension in methanol), amount of catalysts (5 mg, 10 mg and 15 mg) and concentration (1.6 mg L-1, 3.19 mg L(-1)and 6.38 mg L-1) of methylene blue (MB) dye during photodegradation experiments have been investigated. The capacious achievement of AZ1 composite is its reusability and recyclability; it can be reutilized up to three cycles with the same efficiency (100%) while under fourth and fifth cycle, it can degrade off 92.12% and 72.75% MB, respectively. AgNPs may act as a mediator to promote the quick transfer of photo-induced electrons and electron-hole pairs separation in ZIF-11. This work opens a new type of easily fabricated core-shell composites utilizing ZIF-11 for wastewater remediation process.