The reaction of CO₂ with epoxides to produce cyclic carbonates requires high-performance, low-cost, and facilely recycled catalysts. Here, we report a heterogeneous catalyst (MIL-101-N(Bnme₂)Br) based on metal-organic frameworks (MOFs) for catalytic CO₂ conversion into cyclic carbonates. The MIL-101-N(Bnme₂)Br catalyst was prepared as follows: A MOFs precursor (MIL-101-NH₂) was firstly synthesized using a method of hydrothermal synthesis, then coupled with the quaternary ammonium salt ionic liquid (N(BzBnme₂)Br) via aldehyde-amide condensation. A series of comparative experiments revealed that MIL-101-N(Bnme₂)Br catalyst has high activity for catalyzing the cycloaddition reaction to produce cyclic carbonates in the absence of solvents and co-catalysts. As was exampled by the synthesis of propylene carbonate, a high yield (93 %) and selectivity (99 %) was achieved under the optimized conditions (0.93 mol% MIL-101-N(Bnme₂)Br catalyst, 1.4 MPa CO₂ pressure, 17 mmol propylene oxide, 100 °C, 5 h). More impressive, the MIL-101-N(Bnme₂)Br catalyst could be recycled easily by filtration and was reusable up to several times without a significant activity decay. Furthermore, our density functional theory (DFT) calculations suggested that such high catalytic activity mainly resulted from the cooperative catalysis between the coordinatively unsaturated Cr³⁺ sites and Br anions in MIL-101-N(Bnme₂)Br catalyst. Meanwhile, a possible mechanism for the cycloaddition reaction catalyzed by MIL-101-N(Bnme₂)Br catalyst was also proposed.

CO ₂与环氧化物反应生成环状碳酸酯需要高性能、低成本且易于回收的催化剂。在这里，我们报告了一种基于金属有机骨架 (MOF)的多相催化剂 (MIL-101-N(Bnme ₂ )Br)，用于将 CO ₂催化转化为环状碳酸酯。MIL-101-N(Bnme ₂ )Br催化剂的制备如下：首先采用水热合成法合成MOFs前驱体(MIL-101-NH ₂ )，然后与季铵盐离子液体(N( BzBnme ₂ )Br) 通过醛-酰胺缩合。一系列对比实验表明，MIL-101-N(Bnme ₂)Br 催化剂在没有溶剂和助催化剂的情况下催化环加成反应生成环状碳酸酯具有很高的活性。以碳酸亚丙酯的合成为例，在优化条件下（0.93 mol% MIL-101-N(Bnme ₂ )Br催化剂，1.4 MPa CO ₂压力）实现了高产率（93%）和选择性（99%）, 17 mmol 环氧丙烷, 100 °C, 5 h)。更令人印象深刻的是，MIL-101-N(Bnme ₂ )Br 催化剂可以通过过滤轻松回收，并且可以重复使用多次而不会显着降低活性。此外，我们的密度泛函理论 (DFT) 计算表明，如此高的催化活性主要来自配位不饱和 Cr ³⁺之间的协同催化。MIL-101-N(Bnme ₂ )Br 催化剂中的位点和 Br 阴离子。同时，还提出了MIL-101-N(Bnme ₂ )Br催化剂催化环加成反应的可能机理。