Gia-Thanh Vuong

Novel Route to Size-Controlled Fe–MIL-88B–NH2 Metal–Organic Framework Nanocrystals

A new approach for the synthesis of uniform metal-organic framework (MOF) nanocrystals with controlled sizes and aspect ratios has been developed using simultaneously the non-ionic triblock co-polymer F127 and acetic acid as stabilizing and deprotonating agents, respectively. The alkylene oxide segments of the triblock co-polymer can coordinate with metal ions and stabilize MOF nuclei in the early stage of the formation of MOF nanocrystals. Acetic acid can control the deprotonation of carboxylic linkers during the synthesis and, thus, enables the control of the rate of nucleation, leading to the tailoring of the size and aspect ratio (length/width) of nanocrystals. Fe-MIL-88B-NH(2), as an iron-based MOF crystal, was selected as a typical example to illustrate our approach. The results reveal that this approach is used for not only the synthesis of uniform nanocrystals but also the control of the size and aspect ratio of the materials. The size and aspect ratio of nanocrystals increase with an increase in the concentration of acetic acid in the synthetic mixture. The non-ionic triblock co-polymer F127 and acetic acid can be easily removed from the Fe-MIL-88B-NH(2) nanocrystal products by washing with ethanol, and thus, their amine groups are available for practical applications. The approach is expected to synthesize various nanosized carboxylate-based MOF members, such as MIL-53, MIL-89, MIL-100, and MIL-101.

Visible light induced hydrogen generation using a hollow photocatalyst with two cocatalysts separated on two surface sides

A hollow Fe2O3-TiO2-PtOx photocatalyst for visible light H2 generation was prepared from nanosized MIL-88B consisting of coordinatively unsaturated metal centers as a hard template. This photocatalyst is composed of hybrid metal oxide-TiO2 with controllable wall thickness and two different cocatalysts that are separately located on two surface sides.

Direct synthesis and mechanism of the formation of mixed metal Fe2Ni-MIL-88B

The direct synthesis of Fe3-MIL-88B and Fe2Ni-MIL-88B was analyzed using different characterization techniques including UV-vis, IR, and Raman spectroscopies and XRD. It was found that single metal Fe3-MOF-235 seeds which were formed from the first stage of synthesis are precursors for the formation of MIL-88B. Fe3-MOF-235 seeds formed in the first stage of synthesis were then transformed to Fe3-MIL-88B in the case of single metal, and to mixed Fe2Ni-MIL88B in the case of mixed metal synthesis. In the both cases of Fe3-MIL-88B and Fe2Ni-MIL-88B, the FeCl4− anion is a key feature for the formation of MOF-235. An anion-mediated mechanism for the formation of the MOF-235 structure is also suggested.