Metal-organic framework Zr 6 O 4 (OH) 4 (BTC) 2 (HCOO) 6 (MOF-808) nanoparticles were successfully synthesized with a household microwave oven in less than 5 min of irradiation time. The obtained MOF-808 nanoparticles exhibited high superacidity, making them excellent adsorbent for arsenic removal. The adsorption capacity of the as-synthesized MOF-808 nanoparticles for arsenic was 24.83 mg/g. Furthermore, the adsorbents still maintained 82.10% of the removal efficiency after five cycles, indicating that the MOF-808 nanoparticles can serve as a regenerable As(V) adsorbent.
Helong Sun,Lufa Hu,Zhangyang Li,Junyu Lang,Chunling Wang,Xiaohao Liu,Yun Hang Hu,Fangming Jin
Graphical POMs : SiW 12 O x /TiO 2 was demonstrated as an ultra-stable heterogeneous catalyst with tailored molecular interfacial structure and super acidity for photocatalytic oxidation of methane to formic acid. This fabrication method could be relevant for other type POMs based photocatalyst, which provide a way to fabricate ultra-stable molecular interface photo-catalyst with highly efficiency. The interface and surface acidity of heterogeneous catalysts are widely applied to manipulate the catalytic performance. However, the interface structure prepared by traditional synthesis processes required multistep procedures, which was still lack of controllability and stability. Here, we show a general synthetic approach to fabricate ultra-stable heterogeneous catalysts with tailored molecular interfacial structure and super acidity in one step. The as-synthesized SiW 12 O x /TiO 2 catalyst was used for photo-catalytic conversion of methane to value-added oxygenates. We propose that the formed molecular interface W 12 −OH−Ti coupled with the introduced Brønsted acid sites of POMs, results in enhancing the photocatalytic performance. Namely, the addition of SiW 12 O x can reduce the recombination of electrons and holes for triggering charge separation owing to the photoelectron capturing by proton, improving electron transfer to reactants and thereby promoting catalytic activity. This fabrication method provides a way to build molecular interface photo-catalyst by POMs with super acidity and ultra-stable structure.
Investigating proton transport at the interface in an excited state facilitates the mechanistic investigation and utilization of nanomaterials. However, there is a lack of suitable tools for in-situ and interfacial analysis. Here we addresses this gap by in-situ observing the proton transport of graphene quantum dots (GQDs) in an excited state through reduction of magnetic resonance relaxation time. Experimental results, utilizing 0.1 mT ultra-low-field nuclear magnetic resonance relaxometry compatible with a light source, reveal the light-induced proton dissociation and acidity of GQDs’ microenvironment in the excited state (Hammett acidity function: –13.40). Theoretical calculations demonstrate significant acidity enhancement in –OH functionalized GQDs with light induction ( \({{\mathrm{p}}}{K}_{{\text{a}}}^{*}\) = –4.62, stronger than that of H 2 SO 4 ). Simulations highlight the contributions of edge and phenolic –OH groups to proton dissociation. The light-induced superacidic microenvironment of GQDs benefits functionalization and improves the catalytic performances of GQDs. Importantly, this work advances the understanding of interfacial properties of light-induced sp 2 – sp 3 carbon nanostructure and provides a valuable tool for exploring catalyst interfaces in photocatalysis.
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