There is a growing concern for the development of alternative environment friendly sustainable methods for the preparation of nanomaterials. Phytosynthesis of nano zinc aluminate by a microwave method using high purity metal nitrates and Sesamum (Sesamum indicum L.) extract is reported in this work. Sesamum (Sesamum indicum L.) extract simplifies the process and provides an alternative method for a simple and economical way of synthesis of nano zinc aluminate. It is also prepared by conventional method for comparison purpose. The obtained nanomaterials were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), high resolution scanning electron microscopy (HR-SEM), high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), nitrogen adsorption/desorption isotherms, diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy. The formation of pure zinc aluminate phase is confirmed by XRD and FT-IR. The change in morphology from nanoplates to nanoporous sheets from the conventional to microwave heating method is clearly shown by HR-SEM. UV-Visible diffuse reflectance spectroscopy (DRS) studies revealed the band gap energy of ZnAl2O4 nanoplates and nanoporous sheets as 4.0 to 4.2 eV respectively. Photoluminescence (PL) emissions are centered at around 480, 519 and 545 nm, respectively. ZnAl2O4 nanoporous sheets prepared by microwave method showed better catalytic activity for the oxidation benzyl alcohol (90%) than ZnAl2O4 nanoplates prepared by conventional method (51%).