A comparative study on adsorption and photocatalytic dye degradation under visible light irradiation by mesoporous MnO2 modified MCM-41 nanocomposite

• In situ synthesis of meso-MnO2–MCM-41.
• The intra-particle mesoporosity, high textural properties have vital role for an efficient adsorption of dyes such as Rd 6G, MB, MG, Rd B.
• Electron transfer, generation of hydroxyl radical and suitable band gap are the key properties for high degradation of the dyes.

In situ incorporation of semiconducting mesoporous MnO2 (meso-MnO2) into the MCM-41 generates a high surface area meso-MnO2–MCM-41 nanocomposite. The structural, morphological, optical and electronic properties of these catalysts were characterized by low angle and broad angle X-ray diffraction (LXRD and BXRD), X-ray photoelectron spectroscopy (XPS), UV–vis DRS spectroscopy and high resolution transmission electron microscopy (HRTEM). The incorporation of meso-MnO2 into MCM-41 through the silanol group forming nanocomposite has been evidenced from FTIR study and 29Si CP–MAS NMR spectra. Among all the catalysts, meso-MnO2–MCM-41(10) showed the highest surface area (1313 m2 g−1), narrow pore diameter (2.04 nm) and high pore volume (0.86 cm3 g−1). The activity of meso-MnO2–MCM-41 samples were compared towards adsorption and degradation of various cationic dyes such as Rhodamine 6G (Rd 6G), Methylene blue (MB), Malachite green (MG) and Rhodamine B (Rd B). The meso-MnO2–MCM-41(10) composite exhibited 100% photo degradation and adsorption activity towards 100 ppm dye solution in 60 min and 90 min, respectively. The high surface area, narrow pore diameter, high pore volume, intra-particle mesoporosity are responsible for high adsorption. Furthermore, the electron transfer and generation of OH radicals are responsible for the enhancement of photo degradation process.

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