Facile synthesis of ZnO-SnO2 anchored ZIF-8 nanocomposite: a potential photocatalyst
2020
Chandra, Ramesh | Nath, Mala
For the first time, ZnO-SnO₂ nanocomposite has been anchored (ZS@Z) on ZIF-8 (zeolitic imidazolate framework) surface and encapsulated (ZS@Z1, ZS@Z2 and ZS@Z3) within ZIF-8 matrix during the in situ synthesis of ZIF-8. ZnO-SnO₂ nanocomposites were synthesized in various molar ratio of Zn and Sn, i.e. 1:1, 2:8, 4:6, 6:4 and 8:2 (abbreviated as ZS-11, ZS-28, ZS-46, ZS-64 and ZS-82) using sol-gel and by grinding method (abbreviated as ZS-A, ZS-B, ZS-C, ZS-D and ZS-E). As-synthesized ZnO-SnO₂ nanocomposites have been well characterized using various spectroscopic techniques. Further, ZS-E nanocomposite was succesfully anchored and encapsulated within ZIF-8 due to its good photocatalytic activity. Morphology of ZnO-SnO₂ nanocomposites and their composites (ZS@Z, ZS@Z1, ZS@Z2 and ZS@Z3) was ensured by SEM (scanning electron microscopy) and TEM (transmission electron microscopy) images. The lowering of band gap of ZIF-8 from 5.2 to 3.25/3.79 eV confirmed the proper anchored ZnO-SnO₂@ZIF-8. Moreover, XPS analysis was also performed for the analysis of elemental composition of composites. In order to validiate thier photocatalytic application, adsorption capacity and photodegradation efficiency have been examined using methylene blue (MB) as model pollutant. It has been found that 10 mg of ZnO-SnO₂ nanocomposite (ZS-E) exhibits maximum photodegradation efficiency (58.68%) towards MB ([MB] = 1.6 mg L⁻¹) at pH = 7.89 while ZS@Z, ZS@Z1, ZS@Z2 and ZS@Z3 composites (10 mg, 0.5 mg mL⁻¹) can degrade off 100%, 93%, 97% and 92% MB, respectively. Hence, ZS@Z, ZS@Z1, ZS@Z2 and ZS@Z3 composites exhibit enhanced photodegradation efficiency as compared to ZIF-8 and ZnO-SnO₂ nanocomposites and can be used for water remediation.
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