一步法构筑离子液体功能化MOF材料用于常压催化CO2环加成反应

One-pot construction of ionic liquid-functionalized MOF material as the catalyst for CO2 cycloaddition under atmospheric pressure

  • 摘要: 采用原位组装法将羧基离子液体1-丙酸-3-甲基咪唑氯(CFIL)一步固载到一种金属有机框架(MOF)材料NH2-MIL-101上,制备了具有多重活性位点的非均相催化剂NH2-FMOF-CFIL,对其在CO2和环氧氯丙烷的(ECH)环加成反应中的催化性能进行了研究。傅里叶变换红外光谱(FT-IR)和元素分析结果证实离子液体CFIL引入到MOF材料中,粉末X射线衍射(PXRD)、扫描电子显微镜(SEM)和N2吸脱附结果表明离子液体的引入不会破坏NH2-MIL-101的MOF晶体结构或堵塞孔道,但能诱导产生介孔。催化反应表征结果显示,离子液体CFIL结构中咪唑N作为Lewis碱性位点活化CO2,Cl作为亲核试剂促进环氧氯丙烷开环,并与MOF材料NH2-MIL-101上的Cr3+和氨基产生协同作用,诱导在温和条件(0.1 MPa CO2、25–70 ℃、无溶剂和助剂)下,高效催化转化CO2生成氯丙烯碳酸酯,反应24 h氯丙烯碳酸酯收率可达99%,且循环使用5次后,催化剂晶体结构和高活性仍能保持稳定。

     

    Abstract: Carboxylic ionic liquid 1-propionic acid-3-methylimidazolium chloride (CFIL) was immobilized in a metal-organic framework (MOF) material NH2-MIL-101 in one-pot by the in-situ assembly method; as a heterogeneous catalyst with multiple active sites, the catalytic performance of NH2-FMOF-CFIL in the cycloaddition of CO2 with epichlorohydrin (ECH) to synthesize chloropropylene carbonate (CPC) was investigated. The immobilized of CFIL in NH2-MIL-101 was proved by Fourier transform infrared spectroscopy (FT-IR) and elemental analysis, while the powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and N2 adsorption-desorption measurements demonstrated that CFIL neither damages the crystal structure nor blocks the pore of NH2-MIL-101, but induce the formation of mesopores. The catalytic reaction results reveal that there is a catalytic synergy between imidazole N and Cl on CFIL and Cr3+ and amino group on MOF, which endow the NH2-FMOF-CFIL composite excellent catalytic performance in the cycloaddition of CO2 with ECH; under mild conditions, viz., 0.1 MPa CO2, 25–70 ℃ and without using any solvent and cocatalyst, the CPC yield reaches 99% after reaction for 24 h. Moreover, the crystal structure and high activity of the NH2-FMOF-CFIL catalyst are well preserved even after reuse for 5 cycles.

     

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