Bifunctional 3D Cu-MOFs containing glutarates and bipyridyl ligands: Selective CO2 sorption and heterogeneous catalysis

Abstract

We report bifunctional three-dimensional (3D) Cu-MOFs with high selectivity of CO2 over N2 and H2 as well as high catalytic activity for transesterification of esters. The Cu-MOFs containing Cu2 dinuclear units connected by glutarates and bipyridyl ligands are formulated as [{Cu2(Glu)2(μ-bpa)}·(CH 3CN)]n (1) and [{Cu2(Glu)2(μ-bpp) }·(C3H6O)]n (2) (Glu = glutarate, bpa = 1,2-bis(4-pyridyl)ethane, bpp = 1,3-bis(4-pyridyl)propane). These two new bifunctional 3D Cu-MOFs possess very similar pore shape with different pore dimensions. Their gas sorption behaviors were investigated by using CO 2, N2 and H2 at suitable temperatures. Both MOFs exhibited good CO2 selectivity over N2 and H 2. MOF 1 having a smaller pore dimension exhibited much higher CO2 adsorption enthalpy than MOF 2 having a larger pore dimension. However, MOF 2 exhibited more enhanced CO2 uptake ability than MOF 1. A subtle variation of pore dimension indeed influenced the CO2 uptake ability somewhat significantly especially at higher temperatures such as 273 K and 298 K. Heterogeneous catalytic activities of the MOFs were also investigated in detail. Only MOF 1 appeared to be an efficient, mild, and easily recyclable heterogeneous catalyst for the transesterification of esters and constitutes a promising class of heterogeneous catalysts that allowed reuse without a significant loss of activity through twenty runs with ester. © 2012 The Royal Society of Chemistry.