The crystallinity, surface morphology, porosity and band structure of semiconducting catalytic materials greatly influence their photocatalytic efficiency. Here, the semiconducting ZnOs were synthesized with three different synthetic routes of precipitation, solution combustion and direct calcination of precursor. All the synthesized catalysts were characterized thoroughly by X-ray diffraction, Field emission scanning electron microscopy, diffuse reflectance spectroscopy, Brunauer-Emmett-Teller surface area and photoluminescence. The synthesized catalysts show different nano-crystallinity, morphology, surface properties and band structure depending on the synthetic methods. All the synthesized catalysts were explored for photocatalytic degradation of methylene blue under visible and UV light illumination. The correlation between the physical properties and catalytic efficacy were established. The complete mechanism for the photocatalytic degradation of methylene blue was also proposed. The typical band structure and the longer life of excitons due to the presence of defects in solution combustion synthesized ZnO overpowered the other physical properties in influencing the visible and UV light assisted methylene blue degradation. This work shades light on the key controlling factors of a photocatalytic reactions and provides simple strategy for the development of efficient photocatalysts for solar energy conversion applications in solving energy crisis and environmental pollution problems. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.