Revisiting the Incorporation of Ti(IV) in UiO-type Metal-Organic Frameworks: Metal Exchange versus Grafting and Their Implications on Photocatalysis
Revisiting the Incorporation of Ti(IV) in UiO-type Metal-Organic Frameworks: Metal Exchange versus Grafting and Their Implications on Photocatalysis
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DOI：
10.1021/acs.chemmater.7b03320
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发表时间：
2017-11-14
影响因子：
8.6
通讯作者：
Gascon, Jorge
中科院分区：
文献类型：
--
作者：
Santaclara, Jara G.;Olivos-Suarez, Alma I.;Gascon, Jorge
在阳光的作用下从水中生成氢（析氢反应，HER）是设计新能源转换范例的关键挑战。虽然有许多种类的材料可以促进这种反应，但金属有机框架（mof）由于其高表面积、结构多样性和后期可调性而成为有前途的平台。然而，大多数mof存在水解不稳定性，限制了它们在水相HER光催化体系中的应用。UiO系列的3,4 mof具有良好的水稳定性和热稳定性以及合成后改性的机会。5,6 zr - uio型材料功能化的常用策略包括连接剂改性和金属掺入。通过利用功能化配体，前者在uio和mil -125型材料中得到了广泛的研究。10−12例如，MIL-125中对苯二甲酸连接剂的胺化已被证明可以关闭带隙，从紫外线红移，从而实现可见光光催化。在UiO-66的情况下，由于其光可达的未占据Ti （III）状态，Ti （IV）的添加已被广泛研究，但尽管如此，这些材料的结构表征在很大程度上仍然未知。13−18关于Ti如何进入UiO-66的两种假设是通过金属交换进入无机二级构建单元（SBU）或通过连接器空位位点将Ti （IV）接枝到该节点表面（图1）。金属交换主要是用TiCl4·2THF作为Ti （IV）源进行的，但这种交换的性质是
Generation of hydrogen from water (hydrogen evolution reaction, HER) mediated by sunlight is a key challenge in the design of new energy conversion paradigms. 1 While there are many classes of materials that will promote this reaction, metal− organic frameworks (MOFs) have emerged as promising platforms owing to their high surface area, structural diversity, and late-stage tunability. 2 However, most MOFs suffer from hydrolytic instability, limiting their application in aqueous HER photocatalytic systems. 3, 4 MOFs of the UiO series possess good water and thermal stability and opportunities for postsynthetic modification. 5, 6 Common strategies for functionalization of Zr-UiO-type materials include linker modification and metal incorporation. 7− 9 The former has been extensively studied in both UiO-and MIL-125-type materials through utilization of functionalized ligands. 10− 12 For example, amination of the terephthalic acid linker in MIL-125 has been shown to close the band gap, redshifting from the UV and thus enabling visible light photocatalysis. In the case of UiO-66, the addition of Ti (IV) has been extensively studied because of its photoaccessible unoccupied Ti (III) state, but nevertheless, the structural characterization of these materials remains largely unknown. 13− 18The two hypotheses for how incorporation of Ti into UiO-66 occurs are either through metal exchange into the inorganic secondary building unit (SBU) or grafting of the Ti (IV) onto the surface of this node at a linker vacancy site (Figure 1). Metal exchange has been attempted primarily with TiCl4· 2THF as a Ti (IV) source, but the nature of this exchange is