CO2 cycloaddition of styrene oxide over MOF catalysts

Metal organic framework (MOF) structures of UIO-66, UIO-66-NH2, Mg-MOF-74, MIL-101, CuBTC, ZIF-8, IRMOF-3, and MOF-5 having different acid/base properties were prepared and tested for their catalytic activity in the CO2 cycloaddition to styrene epoxide using a high-pressure batch reactor. The high crystallinity and excellent textural properties of the prepared MOF materials were confirmed by XRD and the N-2 adsorption-desorption isotherms at 77 K. Their catalytic cycloaddition activities were found to be well correlated with the Lewis acid/base distributions of the materials examined by NH3- and CO2-TPD, respectively, such that the concurrent presence of Lewis acid and base sites were desirable for high catalytic activity. For a given catalyst weight, UIO-66-NH2 showed the best catalytic performance among the MOF samples tested with close to 100% selectivity to carbonate in chlorobenzene under relatively mild reaction conditions (2.0 MPa, 373 K). UIO-66-NH2 could be reused 3 times without losing catalytic activity in a truly heterogeneous mode without structural deterioration, and it also exhibited excellent cycloaddition activities for different epoxide substrates as well. (C) 2012 Elsevier B.V. All rights reserved.