Tunable Band Gaps in MUV-10(M): A Family of Photoredox-Active MOFs with Earth-Abundant Open Metal Sites
Tunable Band Gaps in MUV-10(M): A Family of Photoredox-Active MOFs with Earth-Abundant Open Metal Sites
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DOI：
10.1021/jacs.1c04808
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发表时间：
2021-08-09
影响因子：
15
通讯作者：
Brozek, Carl K.
中科院分区：
文献类型：
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作者：
Fabrizio, Kevin;Lazarou, Konstantinos A.;Brozek, Carl K.
钛基金属有机框架（Ti-MOFs）由于其能以Ti 3+的形式储存电荷，并能在MOFs-液体界面上通过非均相光氧化还原反应作为助催化剂的光敏剂而受到广泛关注。电荷储存和电荷转移都依赖于MOF和分子基质的氧化还原电位，但控制这些能量方面的因素还没有很好地理解。此外，涉及Ti-MOF的催化剂依赖于助催化剂而不是固有的Ti反应性，部分原因是具有开放金属位点的Ti-MOF是罕见的。在这里，我们报告称，一类的Ti-MOFs被称为MUV-10可以合成修改，包括一系列的氧化还原活性的离子与灵活的协调环境，控制光活性轨道的能量。刘易斯酸性阳离子（Cd 2+、Sr 2+和Ba 2+）安装在MOF簇中或引入到孔中（H+、Li+、Na+、K+）调节MOF的电子结构和带隙。通过使用光学氧化还原指示剂，我们报告的第一个直接测量的费米能级（氧化还原电位）的光激发的MOFs原位。总之，这些结果解释了Ti-MOF存储电荷的能力，并提供了实现具有静电控制的异质光氧化还原化学的设计原理。
Titanium-based metal-organic frameworks (Ti-MOFs) have attracted intense research attention because they can store charges in the form of Ti3+ and they serve as photosensitizers to cocatalysts through heterogeneous photoredox reactions at the MOF-liquid interface. Both the charge storage and charge transfer depend on the redox potentials of the MOF and the molecular substrate, but the factors controlling these energetic aspects are not well understood. Additionally, photocatalysis involving Ti-MOFs relies on cocatalysts rather than the intrinsic Ti reactivity, in part because Ti-MOFs with open metal sites are rare. Here, we report that the class of Ti-MOFs known as MUV-10 can be synthetically modified to include a range of redox-inactive ions with flexible coordination environments that control the energies of the photoactive orbitals. Lewis acidic cations installed in the MOF cluster (Cd2+, Sr2+, and Ba2+) or introduced to the pores (H+, Li+, Na+, K+) tune the electronic structure and band gaps of the MOFs. Through the use of optical redox indicators, we report the first direct measurement of the Fermi levels (redox potentials) of photoexcited MOFs in situ. Taken together, these results explain the ability of Ti-MOFs to store charges and provide design principles for achieving heterogeneous photoredox chemistry with electrostatic control.