Diamine-modified porous indium frameworks with crystalline porous materials (CPM)-5 structure for carbon dioxide fixation under co-catalyst and solvent free conditions.

In the present work, functional diamine groups into indium frameworks to synthesize cyclic carbonates from CO and epoxides with efficient catalytic activity in the absence of co-catalyst and solvent are reported for the first time. Crystalline porous materials (CPM)-5 modified with 1,2-phenylene diamine and ethylene diamine (CPM-5-PhDA and CPM-5-EDA), were prepared using a post-synthetic modification (PSM) method. The properties of the modified CPM-5 were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), N-adsorption, scanning electron microscopy (SEM), CO adsorption, and temperature programmed desorption TPD methods. The presence of diamine groups as basic sites and indium Lewis acid sites in the framework structure were desirable for high catalytic activity. For a given catalyst weight, CPM-5-PhDA was the best candidate to appear with great catalytic activity and selectivity for the cycloaddition reaction at 100°C and 1 MPa CO under co-catalyst and solvent free conditions. CPM-5-PhDA also was found to afford large and bulky epoxides. The catalyst can be easily separated and reused five times without any decline in activity.