蒽基铜MOF的制备及光催化叠氮-炔环加成click反应

Anthracene based copper MOF photocatalytic cycloaddition click reaction of alkyne and azide

摘要:

利用溶剂热法,将Cu(II) 和光敏性的9,10-二(4-羧基苯基)蒽(H2ADBA)通过自组装合成了一例具有光致配体到金属的电子转移(Ligand-to-Metal Charge Transfer; LMCT)行为的二维金属有机框架材料(Metal-Organic Framework; MOF)Cu–ADBA,并通过单晶衍射和PXRD表征了晶体结构。SEM、TEM、AFM表明Cu–ADBA在溶液中可以发生剥离,形成约4 nm厚的薄片,有利于暴露出更多的催化位点,UV-Vis表明配体H2ADBA在350-410 nm具有良好的吸收,激发态还原电位-1.56 V (vs. Ag/AgCl),足以还原Cu–ADBA金属节点的Cu(II),荧光光谱表明Cu–ADBA的荧光强度远小于配体,Raman波谱、XPS光电子能谱和EPR 波谱表明光照下,MOF中的配体受到激发,会将金属节点中的Cu(II) 还原为Cu(I)。在365 nm LED 光照下,以葡萄糖为电子牺牲剂,Cu–ADBA可以高效催化炔烃和苄基叠氮的环加成click反应,催化剂可以重复使用3次并且仍保持较高的催化活性。

Abstract:

Self-assembly between Cu(II) and photoredox 4,4"-(anthracene-9,10-diyl)dibenzoic acid constructs a new 2D metal organic framework Cu–ADBA with photoinduced LMCT (Ligand-to-Metal Charge Transfer) behavior using solvothermal method, and the crystal structure has been characterized by single-crystal diffraction and PXRD. SEM, TEM, and AFM measurements indicate that Cu–ADBA in solution can be exfoliated and form nanosheets with 4nm thickness, which is favorable to expose more catalytic sites. UV-Vis showed that the ligand H2ADBA has a wide absorption band between 350 and 410 nm, the excited state reduction potential of H2ADBA was -1.56 V (vs. Ag/AgCl), which is able to reduce Cu(II) in the metal node of Cu–ADBA. The fluorescence spectrum shows that the fluorescence intensity of Cu–ADBA is much smaller than that of the ligand, and the Raman spectrum, XPS photoelectron spectra and EPR spectra show that the ligand in MOF was excited under the illumination, which reduces the Cu(II) in the metal node to Cu(I). Under 365 nm LED light, the cycloaddition click reaction of alkynes and benzyl azides was efficiently catalyzed by Cu–ADBA with glucose as the electron-sacrificing agent, and the catalysts could be reused for three times without obvious deactivation.