Engineering highly effective and stable nanocomposite photocatalyst based on NH 2 -MIL-125 encirclement with Ag 3 PO 4 nanoparticles Reda M. Abdelhameed a, *, David Maria Tobaldi b , Mohamed Karmaoui c, * a Applied Organic Chemistry Department, Chemical Industries Research Division, National Research Centre, 33 EL Buhouth St., Dokki, Giza 12311, Egypt b Department of Materials and Ceramic Engineering/CICECO—Aveiro Institute of Materials, University of Aveiro, Campus Universita’rio de Santiago, 3810-193 Aveiro, Portugal c School of Chemistry, College of Engineering and Physical Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK A R T I C L E I N F O Article history: Received 23 June 2017 Received in revised form 20 August 2017 Accepted 7 October 2017 Available online 9 October 2017 Keywords: New dry-synthesis process Metal organic framework nanocomposite/Ag 3 PO 4 NPs@NH 2 -MIL-125 Photocatalytic activity Photostability properties A B S T R A C T The development of highly efficient photocatalyst under visible light still a challenge. Herein we present band gap modification of NH 2 -MIL-125 by encirclement with suitable semiconductor that possesses a narrow band gap Ag 3 PO 4 nanoparticles (NPs). The band gap of NH 2 -MIL-125 was decreased from 2.51 to 2.39 eV, making them potential candidates for photocatalytic applications. Our prepared photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). TEM characterizations indicated that NH 2 -MIL-125 MOFs are coated with Ag 3 PO 4 NPs. The photocatalytic activity (PCA) was evaluated in the liquid-solid phase, by monitoring the degradation of an organic dye (methylene blue (MB) and rhodamine-B (RhB)) under visible-light irradiation. Furthermore, the Ag 3 PO 4 @NH 2 -MIL-125 nanocomposites shown themselves to be the most active with the reaction rate being 39 and 35 times higher than the well known Degussa P25 TiO 2 toward photocatalytic degradation of MB and RhB. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Engineering visible-light response semiconductors are very important in designing efficient photocatalysts [1–11]. In general, the most used photocatalyst is TiO 2 because it is chemically stable, non toxic and it possesses strong oxidizing ability of photo induced holes [12]. On the other hand, the most significant drawback of TiO 2 as a photocatalyst– in its anatase modification  is its wide optical band gap (E g = 3.2 eV), this making the photocatalytic reaction triggered only by UV-A radiation. Therefore, researchers made great efforts to extend the photo-response to the visible light region by, among other things, coupling TiO 2 with narrow band gap E g semiconductors [13–16]. Ag 3 PO 4 NPs is one of the best known narrow band gap E g (2.45 eV) semiconductor and it has good photocatalytic activity (PCA) in visible region [17], but its efficiency is relatively low due to inherent fast charge recombination. Moreover, the greatest drawback of Ag 3 PO 4 NPs as photocatalyst is that they are prone to be self-reduced into silver during the photocatalytic reaction [17–20]. Besides, in Ag 3 PO 4 , the potential of the conduction band (CB) is more positive than that of reduction potential of O 2 [21]. This implies that generated electrons do not react efficiently with molecule adsorbed on the surface of the photocatalyst, hindering its performance in the PC process and decreasing the stability of that photocatalyst [22]. Metal organic frameworks (MOFs) are porous sponge-like crystalline materials. MOFs are usually prepared from inorganic salts and multi dentate organic linkers producing one-, two-, or three-dimensional networks [23]. MOFs have unique properties such as large surface areas and a variety of chemical functionalities [24]. MOFs are used in many fields of research, such as gas storage [25], adsorption/separation [26–28], water treatment [29], building light emitters [30,31], functionalized textile[32] and catalysis [30,33]. NH 2 -MIL-125(Ti) is TiO 2 -organic framework, it is synthesized from 2-aminoterphthalic acid and titanium isopropoxide via a solvothermal route. The structure of NH 2 -MIL-125(Ti) have two types of cages corresponding to the octahedral (12.55 Å) and tetrahedral ( 6.13 Å) vacancies of a cubic close-packed (ccp) with triangular narrow windows (5–7 Å) * Corresponding authors. E-mail addresses: reda_nrc@yahoo.com (R.M. Abdelhameed), m.karmaoui@bham.ac.uk (M. Karmaoui). https://doi.org/10.1016/j.jphotochem.2017.10.011 1010-6030/© 2017 Elsevier B.V. All rights reserved. Journal of Photochemistry and Photobiology A: Chemistry 351 (2018) 50–58 Contents lists available at ScienceDirect Journal of Photochemistry and Photobiology A: Chemistry journal home page : www.elsevier.com/locat e/jphotochem