Porous metal-organic framework with Lewis acid - base bifunctional sites for high efficient CO2 adsorption and catalytic conversion to cyclic carbonates

A highly porous three-dimensional (3D) metal-organic framework (MOF) [Ni-3(BTC)(2)(MA)(H2O)](DMF)(7) (1) incorporating both exposed metal sites and nitrogen-rich melamine was successfully constructed via solvothermal assembly of 1,3,5-benzenetricarboxylic acid (H3BTC), melamine (MA) and Ni(II) ions. The resulting activated Ni(II)-MOF-1a features high CO2 loading capacity and excellent CO2 affinity due to the Lewis-base property together with abundant micropores. The heterogeneous catalytic activity of the activated Ni(II)-MOF-1a was confirmed by remarkably high efficiency on CO2 cycloaddition with small epoxides under ambient conditions. Moreover, the Ni(II)-MOF-1a exhibited satisfied stability and versatility, and it was easy to recycle with no obvious decrease of catalytic activity. Then the feasible synergistic mechanism of Ni(II)-MOF/Bu4NBr catalysts for CO2 conversion was proposed.