Mancuso Jenna L, Fabrizio Kevin, Brozek Carl K, Hendon Christopher H
Department of Chemistry and Biochemistry, University of Oregon Eugene OR 97403 USA
Chem Sci. 2021 Jul 30;12(35):11779-11785. doi: 10.1039/d1sc03019a. eCollection 2021 Sep 15.
Ti-containing metal-organic frameworks are known to accumulate electrons in their conduction bands, accompanied by protons, when irradiated in the presence of alcohols. The archetypal system, MIL-125, was recently shown to reach a limit of 2e per Ti octomeric node. However, the origin of this limit and the broader applicability of this unique chemistry relies not only on the presence of Ti, but also access to inorganic inner-sphere Lewis basic anions in the MOF nodes. Here, we study the loading of protons and electrons in MIL-125, and assess the thermodynamic limit of doping these materials. We find that the limit is determined by the reduction potential of protons: in high charging regimes the MOF exceeds the H/H potential. Generally, we offer the design principle that inorganic anions in MOF nodes can host adatomic protons, which may stabilize meta-stable low valent transition metals. This approach highlights the unique chemistry afforded by MOFs built from inorganic clusters, and provides one avenue to developing novel catalytic scaffolds for hydrogen evolution and transfer hydrogenation.
含钛金属有机框架在醇类存在下受到辐照时，已知会在其导带中积累电子，并伴有质子。典型体系MIL - 125最近被证明每个钛八聚体节点的电子积累极限为2个电子。然而，这一极限的起源以及这种独特化学性质的更广泛适用性不仅取决于钛的存在，还取决于在金属有机框架节点中获取无机内球层路易斯碱性阴离子。在此，我们研究了MIL - 125中质子和电子的负载情况，并评估了这些材料掺杂的热力学极限。我们发现该极限由质子的还原电位决定：在高电荷状态下，金属有机框架超过了H/H电位。一般来说，我们提出了一种设计原则，即金属有机框架节点中的无机阴离子可以容纳吸附原子态的质子，这可能会稳定亚稳态低价过渡金属。这种方法突出了由无机簇构建的金属有机框架所提供的独特化学性质，并为开发用于析氢和转移氢化的新型催化支架提供了一条途径。
