Core-Shell Structured NH2-UiO-66@TiO2 Photocatalyst for the Degradation of Toluene under Visible Light Irradiation
Core-Shell Structured NH2-UiO-66@TiO2 Photocatalyst for the Degradation of Toluene under Visible Light Irradiation
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核壳结构NH2-UiO-66@TiO2光催化剂可见光降解甲苯
DOI：
10.3866/pku.whxb202009045
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发表时间：
2020
影响因子：
10.9
通讯作者：
Wu Zhongbiao
中科院分区：
文献类型：
--
作者：
Zhou Yi;Ouyang Weilong;Wang Yuejun;Wang Haiqiang;Wu Zhongbiao
金属有机框架（MOFs）对于使用可见光的光致发光具有重要意义，但它们通常受到光激发对的不稳定性和高复合率的限制。将MOFs集成到无机半导体中是促进其活性的最普遍的方法之一。本文合成了一种核壳结构的MOF@TiO2（NH 2 -UiO-66@TiO2）光催化剂，用于甲苯的降解。采用水热法合成了NH 2 -UiO-66作为核，然后在其表面包覆一层非晶态TiO 2壳层。与NH 2-UiO-66和其他直接混合制备的样品相比，NH 2-UiO-66@TiO2对甲苯的降解率更高.以NH 2 -UiO-66@TiO2为催化剂，甲苯的降解率在3 h内达到76.7%，是NH 2 -UiO-66的1.48倍.降解性能在4次重复使用实验中也保持稳定，轻微失活经乙醇洗涤后重新激活。采用X射线衍射（XRD）、X射线光电子能谱（XPS）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）等表征手段对NH 2 -UiO-66@TiO 2的物理化学性质进行了研究。利用测定的理化性质，探讨了NH 2 -UiO-66@TiO2的光催化机理. NH 2 -UiO-66是一种理想的光催化剂，具有可见光响应和巨大的比表面积（914.9m2·g-1），有利于太阳光的利用和室内空气中污染物的吸收。此外，NH 2 -UiO-66与TiO 2之间形成了一个新的界面，有效地拓宽了光吸收区，提高了光生物种的利用率。光生空穴和电子一旦形成就可以通过中间层传输。推测空穴将转移到NH 2 -UiO-66的HOMO上，然后与H2 O分子联合收割机结合形成羟基自由基（·OH）.同时，更多的电子倾向于与TiO 2导带中的氧分子联合收割机结合，而不是与空穴重新联合收割机结合。因此，电子和空穴的复合率降低，而氧自由基和羟基自由基的数量增加。甲苯被这两种自由基有效地氧化。NH 2 -UiO-66@TiO2的合成策略是一条有效的途径。这一工作为设计核壳结构的MOF@光催化剂降解室内空气污染物提供了新的思路。
: Metal-organic frameworks (MOFs) are of significant interest for photocatalysis using visible light, but they are typically limited by the instability and high recombination ratio of photoexcited pairs. Integrating MOFs into an inorganic semiconductor is one of the most widespread methods to promote their activity. In this study, a core-shell structured MOF@TiO 2 (NH 2 -UiO-66@TiO 2 ) was synthesized as an efficient photocatalyst for the degradation of toluene. Pristine NH 2 -UiO-66 was synthesized by a hydrothermal method as the core, which was then coated with an amorphous TiO 2 shell. Compared with pristine NH 2 -UiO-66 and other samples prepared by the direct mixing of NH 2 -UiO-66 and TiO 2 , NH 2 -UiO-66@TiO 2 exhibited a higher degradation rate of toluene. Using NH 2 -UiO-66@TiO 2 as a catalyst, the degradation efficiency of toluene reached 76.7% within 3 h, which is 1.48 times higher than that of NH 2 -UiO-66. The degradation performance was also stable in four repeated reuse experiments, and the slight deactivation was reactivated after washing with ethanol. A series of characterization methods were used to determine the physicochemical properties of NH 2 -UiO-66@TiO 2 , including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Using the measured physicochemical properties, the photocatalytic mechanism of NH 2 -UiO-66@TiO 2 was explored. NH 2 -UiO-66 is an ideal photocatalyst, with visible-light response and a huge specific surface area (914.9 m 2 ·g − 1 ), which is favorable for the utilization of sunlight as well as the absorption of pollutants in indoor air. In addition, a new interface formed between the two components (NH 2 -UiO-66 and TiO 2 ), which efficiently broaden the light absorption area and enhanced the utilization of photogenerated species. The photogenerated holes and electrons could transfer through the interlayer as soon as they were formed. It is speculated that holes would transfer to the HOMO of NH 2 -UiO-66, and then combine with H 2 O molecules to form hydroxyl radicals (·OH). At the same time, more electrons tended to combine with oxygen molecules in the conduction band of TiO 2 rather than recombine with holes. Consequently, the recombination rate of electrons and holes decreased, while the quantity of oxygen radicals and hydroxyl radicals increased. Toluene was efficiently oxidized by these two types of radicals. Owing to the outstanding properties mentioned above, the strategy of constructing NH 2 -UiO-66@TiO 2 is considered to be an effective approach. This work may provide new insights into the design of core-shell structured MOF@photocatalysts for the photocatalytic degradation of indoor air pollutants.