The catalytic hydrogenation has been widely applied in biology and chemistry fields. In the last decades, most of the catalytic hydrogenation reactions relay on the expensive and toxic platinum group metal complexes. The "frustrated Lewis pair" (FLPs) avoid the disadvantages of the traditional novel metal catalyst and provides an efficient metal-free catalysis route to realize the hydrogenation of many types of unsaturated compounds, yet the unsatisfactory recyclability of most of the FLPs largely restricting their potential applications. Grafting the FLPs into porous materials would be a short-cut method to obtain porous FLPs with good recycling performance and catalytic efficiency. As one kind of crystalline porous materials, metal-organic frameworks (MOFs) have shown enormous potential in catalysis areas due to their well-defined yet tunable pores and functionalized walls. The suitable pore size, high surface area and spacious pore space of MOFs can provide the substrate molecules enough accessibility with the catalytic centers inside MOFs. Therefore, introducing the FLPs into MOFs would give a new kind of porous frustrated Lewis pairs with great catalytic hydrogenation performance and recyclability. In this work, we designed and successfully constructed the porous MOF-FLPs as a highly active heterogeneous catalyst for the hydrogenation of imine compounds. To incorporate the FLP into MOF, we chose a Lewis base (LB) with two potential coordination sites to construct a MOF-LB first, and then constructed the porous MOF-FLP through the reaction between MOF-LB and Lewis acid. The porous MOF-FLP shows high surface area and big pore size, which allowed the excess of the substrates in the catalytic reaction. Given the strong coordination interaction between Lewis base and MOF, the FLP is stabilized thereby exhibiting efficient catalytic activity for catalytic reduction of imines with excellent recyclability. The porous MOF-FLP exhibits interesting size and steric selectivity in the catalytic reduction reactions as a result of the confinement imparted by the porous framework structure of MOF. In particular, the MOF-FLP showed great performance on the chemoselective hydrogenation of α, β-unsaturated imines, which benefited their binding environment in the pores. Considering the broad applicability of FLPs, our work thus lays a foundation for developing MOF-FLP as one kind of high-efficient catalyst.

Metal-organic frameworks-based porous frustrated lewis pairs as the new heterogeneous hydrogenation catalyst

2019 Spring National Meeting

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