Zhang Chenxi, Lei Da, Xie Chenfan, Hang Xiaoshuai, He Chuanxin, Jiang Hai-Long
College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, 518060, P. R. China.
Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Soft Matter Chemistry, Department of Chemistry, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China.
Adv Mater. 2021 Dec;33(51):e2106308. doi: 10.1002/adma.202106308. Epub 2021 Oct 13.
The built-in electric field can be generated in the piezoelectric materials under mechanical stress. The resulting piezoelectric effect is beneficial to charge separation in photocatalysis. Meanwhile, the mechanical stress usually gives rise to accelerated mass transfer and enhanced catalytic activity. Unfortunately, it remains a challenge to differentiate the contribution of these two factors to catalytic performance. Herein, for the first time, isostructural metal-organic frameworks (MOFs), i.e., UiO-66-NH (Zr) and UiO-66-NH (Hf), are adopted for piezo-photocatalysis. Both MOFs, featuring the same structures except for diverse Zr/Hf-oxo clusters, possess distinctly different piezoelectric properties. Strikingly, UiO-66-NH (Hf) exhibits ≈2.2 times of activity compared with that of UiO-66-NH (Zr) under simultaneous light and ultrasonic irradiation, though both MOFs display similar activity in the photocatalytic H production without ultrasonic irradiation. Given their similar pore features and mass transfer behaviors, the activity difference is unambiguously assignable to the piezoelectric effect. As a result, the contributions of the piezoelectric effect to the piezo-photocatalysis can be clearly distinguished owing to the stronger piezoelectric property of UiO-66-NH (Hf).
在机械应力作用下，压电材料中可产生内建电场。由此产生的压电效应有利于光催化中的电荷分离。同时，机械应力通常会导致传质加速和催化活性增强。不幸的是，区分这两个因素对催化性能的贡献仍然是一个挑战。在此，首次采用同构金属有机框架（MOF），即UiO-66-NH（Zr）和UiO-66-NH（Hf）进行压电光催化。除了不同的Zr/Hf-氧簇外，这两种MOF具有相同的结构，但具有明显不同的压电性能。引人注目的是，在同时光照和超声辐照下，UiO-66-NH（Hf）的活性约为UiO-66-NH（Zr）的2.2倍，尽管在没有超声辐照的光催化产氢中，这两种MOF表现出相似的活性。鉴于它们相似的孔特征和传质行为，活性差异明确可归因于压电效应。因此，由于UiO-66-NH（Hf）具有更强的压电性能，压电效应在压电光催化中的贡献可以得到清晰区分。
