Co(II)-MOF: A Highly Efficient Organic Oxidation Catalyst with Open Metal Sites

A porous Co­(II)-MOF (1) was synthesized by the combination of a bent imidazole-bridged ligand and p-phthalic acid (PTA) with Co­(OAc)2 under solvothermal conditions. This Co­(II)-MOF (1) is able to undergo a reversible MeOH substitution reaction on the Co­(II) center via a single-crystal-to-single-crystal process. The desolvated Co­(II)-MOF (2) with the open Co­(II) sites is very stable (up to 350 °C). Furthermore, 2 is a highly active heterogeneous catalyst for various organic substrates oxidation in the presence of tert-butyl hydroperoxide (TBHP) under milder conditions. The importance of open Co­(II) sites in 2 for the organic substrates oxidation is directly evidenced by the single-crystal X-ray diffraction.本研究通过溶剂热法，将弯折型咪唑桥联配体、对苯二甲酸(PTA)与乙酸钴(II)进行反应，合成了多孔Co(II)金属有机框架(MOF, Metal-Organic Framework)1。该Co(II)金属有机框架(1)可通过单晶到单晶转变过程，在Co(II)金属中心发生可逆的甲醇(MeOH)取代反应。带有开放Co(II)位点的脱溶剂化Co(II)金属有机框架(2)具有极佳的热稳定性，热稳定温度可达350 ℃。此外，在叔丁基过氧化氢(TBHP)存在的温和反应条件下，框架2对多种有机底物的氧化反应展现出优异的多相催化活性。单晶X射线衍射实验直接证实了框架2中开放Co(II)位点在有机底物氧化反应中的关键作用。