Chemical Fixation of CO2 and Other Heterogeneous Catalytic Studies by Employing a Layered Cu-Porphyrin Prepared Through Single-Crystal to Single-Crystal Exchange of a Zn Analogue.

Abstract

A solvothermal reaction of Zn(NO3 )2 ⋅6 H2 O, tetra-(4-pyridyl)porphyrin (H2 TPyP), and 4,4'-oxybis(benzoic acid) (H2 OBA) resulted in a new two-dimensional Zn- porphyrin metal-organic framework compound, [Zn2 (C40 H24 N8 )0.5 (C14 H8 O5 )(DMA)](DMA)(H2 O)6 (1; DMA=N,N-dimethylacetamide). The ZnII ions present in 1 could be exchanged by using a solution of Cu(NO3 )2 ⋅3 H2 O in DMA at room temperature to give [Cu2 (C40 H24 N8 )0.5 (C14 H8 O5 )(DMA)](DMA)(H2 O)3 (Cu∈1). The extra-framework solvent molecules have been shown to be reversibly removed or exchanged without collapse of the framework. Solvent-free Cu∈1 was explored as an active heterogeneous catalyst towards three different organic reactions: 1) the chemical fixation of CO2 into cyclic carbonate at room temperature and 1 atm; 2) the nitroaldol reaction under solvent-free conditions, and 3) the three-component coupling of aminopyridine, benzaldehyde, and aryl alkynes followed by 5-exo-dig cyclization to produce the important pharmacophore imidazopyridine.