Triethylamine as a tuning agent of the MIL-125 particle morphology and its effect on the photocatalytic activity
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Triethylamine as a tuning agent of the MIL-125 particle morphology and its effect on the photocatalytic activity Nicolás Artemio Rodríguez1,2 · Rodrigo Parra1,3 · María Alejandra Grela1,2 Received: 31 July 2020 / Accepted: 13 October 2020 © Springer Nature Switzerland AG 2020
Abstract MIL-125 is prepared using a modified version of a previously reported strategy, in which different ratios of trimethylamine (TEA) are added to the reaction mixture. It is shown that TEA made the synthesis of MIL-125 more feasible, at lower temperatures, and limiting the formation of TiO2. The solids are then characterized by various means and finally studied in the photodegradation of Rhodamine B (RhB). The shape and size of MIL-125 particles can be tuned by varying the number of TEA equivalents, with the smallest particles yielding the highest rate of RhB decomposition. It is found that the adsorption of the photocatalyst on MIL-125 plays an important role in the photodegradation mechanism of the dye. Keywords Metal-Organic Frameworks · Photocatalysis · Particle morphology · MIL-125
1 Introduction Metal-Organic Frameworks (MOFs) are a class of materials with promising properties for many applications [1–3], ranging from gas storage [4] to heterogeneous photocatalysis [5–7]. However, the synthesis and stability of MOFs are still subject to continuous analysis [7–9]. Some of these materials present weak interactions between the metal (or metallic cluster) and the ligands, which makes them prone to hydrolysis, as it is the case of Zn-based MOFs. Nevertheless, these Zn-based materials were the first MOFs to be synthesized at the end of the twentieth century and from their study much insight was gained regarding their strikingly high surface areas [4], the possibility of tuning their properties [10], and some ways to inhibit the hydrolysis of these materials [11].
Other kinds of MOFs were prepared in the years following the first reports. In particular, Ti-based MOFs are interesting because of their higher stability in water or humid conditions, compared to those synthesized using Zn precursors. Dan-Hardi et al. [12] prepared in 2009 a MOF using a Ti precursor for the first time, MIL-125. The synthesis of MIL-125 involved the solvothermal reaction of a mixture of titanium (IV) isopropoxide and terephthalic acid (H2BDC) in N,N-dimethylformamide (DMF) and methanol. However, it was recognized that the product obtained by this method contained impurities of TiO2 [12]. In 2013 Hendon et al. [13] obtained MIL-125 by a new strategy, which involved the synthesis of a Ti-oxocluster coordinated by pivalic acid. This solid was then mixed with H2BDC in DMF and methanol and heated to obtain MIL-125.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s42452-020-03683-1) contains supplementary material, which is available to authorized users. * Nicolás Artemio Rodríguez, [email protected] | 1Departamento de Química, Facultad de Ciencias Exactas y Naturales (FCEyN), Universidad Nacional d
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