Fabrication of mesoporous CuO/ZrO 2 -MCM-41 nanocomposites for photocatalytic reduction of Cr(VI) Binita Nanda a,⇑ , Amaresh C. Pradhan b , K.M. Parida a,⇑ a Centre for Nano Science and Nano Technology, Siksha ‘O’ Anusandhan University, Khandagiri, Bhubaneswar 751030, Odisha, India b UNAM-National Nanotechnology Research Center, Bilkent University, Ankara 06800, Turkey highlights  Mesoporous ZrO 2 –MCM- 41synthesized by in situ incorporation process.  CuO@ZM-41 synthesized by modification of CuO onto the ZrO 2 – MCM-41.  CuO@ZM-41nacomposite shows semiconductor behavior and mesoporosity.  High surface area, lower e  and h + recombination are enhancing the photo-reduction. graphical abstract Mesoporous nanocomposite (CuO@ZM-41) is synthesized by incorporating mesoporous ZrO 2 (Z) into MCM-41 (M-41) framework followed by loading of CuO by wetness impregnation method. The synergism between CuO and the support material mesoporous ZM-41 and efficient light absorption on the surface of the composite is the key factor for the reduction Cr 6+ to Cr 3+ within 30 min time. article info Article history: Received 25 July 2016 Received in revised form 12 October 2016 Accepted 10 November 2016 Available online 16 February 2017 Keywords: CuO/ZrO 2 –MCM-41 Nanocomposites Synergistic effect Photo-reduction abstract Mesoporous nanocomposites of CuO/ZrO 2 –MCM-41 (CuO@ZM-41) was designed by incorporating meso- porous ZrO 2 (Z) into the high surface area MCM-41 (M-41) framework followed by loading CuO by wet- ness impregnation method keeping Si/Zr ratio 10. The nanocomposites were studied under PXRD, N 2 sorption, DRS spectra, FTIR, XPS, NMR, HRTEM and PL to evaluate structural, morphological, optical prop- erties and also the mesoporosity nature of the samples. The photo-reduction of Cr 6+ was performed over CuO@ZM-41 by varying pH, substrate concentration, and irradiation time and catalyst dose. Among all the catalysts, 2 CuO@ZM-41 was found to be efficient photocatalyst for the photo-reduction of Cr 6+ . Nearly 100% reduction of Cr 6+ has been achieved by 2 CuO@ZM-41 within 30 min. Intra-particle meso- porosity, high surface area, presence of CuO nanorods and electron transfer properties are the key factors for enhancing the photo-reduction activity of 2CuO@ZM-41. Ó 2016 Elsevier B.V. All rights reserved. 1. Introduction Over the decade, the extensive use of heavy metal in chemical industries for electroplating, leather tanning, paint processes and mining etc. has become a great concern [1]. It is non- biodegradable, but increases its concentration from one tropic level to other by biomagnification [2]. In nature Cr occurs in a vari- http://dx.doi.org/10.1016/j.cej.2016.11.080 1385-8947/Ó 2016 Elsevier B.V. All rights reserved. ⇑ Corresponding authors at: Department of Chemistry, Centre for Nano Science and Nano Technology, Siksha ‘O’ Anusandhan University, Khandagiri, Bhubaneswar 751030, Odisha, India (K.M. Parida). E-mail addresses: kulamaniparida@soauniversity.ac.in, paridakulamani@yahoo. com (K.M. Parida). Chemical Engineering Journal 316 (2017) 1122–1135 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej