Structure modulation, selective dye adsorption and catalytic CO2 transformation of four pillared-layer metal-organic frameworks

In this paper, a series of metal-organic frameworks (MOFs), namely, [Co(pip)(4,4′-bpy)]n (1), [Co2(pip)2(bibp)]n (2), [Mn(pip)bidmp]n (3) and [Ni(pip)(bibp)(H2O)]n (4) (bpy ​= ​4,4′-bipyridine, bibp ​= ​4,4-bis(imidazolyl)biphenyl, bidmb ​= ​1,4-bis(1-imidazoly)-2,5-dimethylbenzene), have been solvothermally synthesized based on the main ligand 6-(3-pyridyl)isophthalic acid (H2pip) and structurally characterized by various methods. These MOFs all present three dimensional (3D) pillared-layer frameworks, and through systematic modulation of auxiliary ligands and metal ions, their structures can be well regulated from nonporous to porous. Considering their excellent thermal and water stability, the dye removal properties from water solutions of these MOFs were further studied, and notably, 2 which has the largest porosity of the four MOFs, exhibits very fast selective adsorption of methyl orange over Rhodamine B (MO/RhB) with a total MO uptake amount of 83.4 ​mg ​g−1. Moreover, the catalytic CO2 transformation properties of these MOFs were also carried out under mild conditions, of which 2 exhibited the highest catalytic activity with 69.57% yield for propylene carbonate and 50.55% for butylene carbonate, respectively.