24 A mesoporous ZnFe 2 O 4 nanoparticles prepared as a visible light responsive catalyst, the 25 morphology, structure and optical property of the spinel oxide are characterised, diligently. 26 Photocatalytic activity of ZnFe 2 O 4 nanoparticles assessed toward the oxidation of gaseous 27 benzene. A comparative study conducted, between ZnFe 2 O 4 and Fe 2 O 3 , in terms of water and 28 benzene adsorption using microcalorimetry as well as photocatalytic benzene oxidation. In this 29 context, ZnFe 2 O 4 showed greater activity than Fe 2 O 3 . The heats of water adsorption for the 30 spinel and hematite are -270 kJ/mol and -190 kJ/mol, respectively; revealing the dissociative 31 mode of the adsorption, which is crucial for the generation of hydroxyl radicals. Moreover, the 32 heat of benzene adsorption for ZnFe 2 O 4 and Fe 2 O 3 are -167 kJ/mol and -139 kJ/mol, 33 respectively. Finally, the intermediate (phenol) and products (H 2 & CO 2 ) of the oxidation 34 reaction is monitored by GC (FID/TCD) and DRIFT: a mechanism is proposed accordingly for 35 the photocatalytic oxidation of the benzene. 36 37 Keywords: ZnFe 2 O 4 ; Fe 2 O 3 ; Gaseous benzene; Visible-light photocatalysis; Adsorption of 38 water; Hydroxyl radicals. 39 40VOCs with a high oxidation potential and sorely stable structure that makes it a proper choice as 47 an organic reactant to evaluate the photocatalytic property of semiconductors, compare to dyes 48 that are easily photo-oxidised due to their lower oxidation potential [4,5]. A limited number of 49 publications are reported about the gas-phase photocatalytic oxidation of benzene under visible 50 light irradiation [6][7][8][9][10][11]. Consequently, preparation of stable and low-cost semiconductors with 51 narrow bandgap energy to absorb a large number of solar energy is vital [12]. In this context, 52 hematite (Fe 2 O 3 ) is the most thermodynamically stable iron oxide phases at ambient temperature 53 and it has narrow band gap energy (2.2 eV) [13]. However, hematite has its own disadvantages 54 due to poor conductivity, high charge recombination rates and short hole diffusion length (2-4 55 nm) [14][15][16]. Encountering these issues, semiconductors consisting of two or more distinct 56 semiconductor components have become a focus of intense research due to their unique and 57 enhanced performances nanoparticle [17][18][19][20]. In such case, spinel oxides have attracted great 58 interest for catalytic reactions due to their desirable properties, such as single crystal shape, high 59 thermal stability, and well diffused, etc. [21][22][23][24]. ZnFe 2 O 4 is an n-type semiconductor and one of 60 the most promising spinel system materials [25]. It has been investigated in many applications, 61 such as photocatalysis, magnetic resonance imaging, drug delivery technology and gas sensor 62 due to its low cost, eco-friendly and photo-corrosion resistant advantages [26][27][28]. In spite of the 63 great potential, there have been only limited studies of these materials, mainly as a 64 supplementary co...

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The visible light response and photocatalytic activities of covalently bonded iron(III)-Schiff base complex is evaluated by photooxidation of nitric oxide under visible light exposure. In addition, this study reports the existing of dominant active sites on the surface of grafted complex toward water adsorption, which leads to the generation of hydroxyl radicals under illumination. Moreover, the morphological analysis exhibits high surface area (575 m 2 /g) with an average pore diameter of 21 nm; in this context, XRD analysis shows that the characteristic peaks of the Schiff-base complex are covered by the amorphous structure of the silica network, however, the microscopic analysis reveals the irregular shape of the grafted catalyst. Furthermore, the catalytic activity was evaluated by photooxidation of reactive blue 13 dye in aqueous solution under ambient light illumination. Also, the reaction variables such as the amount of catalyst, pH value, concentration and temperature of the dye solution were studied and discussed in detail. It seems, the enhanced activity of the photocatalyst toward the dye decolourization is a consequence of its uniform surface, large surface area, fine particles and active surface for the water adsorption.