The exquisite combination of [Tb2(CO2)9] units and [Tb2(CO2)6(HCO2)(H2O)2]n chains under acidic solvothermal condition generated a highly robust {(Me2NH2)4[Tb4(DDAC)3(HCO2)(OH2)2]⋅6DMF⋅5H2O}n (SLU-1, H5DDAC = 2,6-di(3,5-dicarboxylphenyl)-4-aminobenzoic acid) microporous framework. In SLU-1, each four [Tb(1)2(CO2)9] units and four [Tb(2)2(CO2)6(H2O)2] units are bridged by eight DDAC5− ligands to form cage-like voids with the diameter of 8.2 Å and the moderate window size of 4.2 × 3.5 − 4.6 × 5.5 Å2. which is concurrently functionalized by amino groups on the inner surface. More interestingly, the inner surface of cage-like voids in activated SLU-1a is functionalized by free amino groups and rich unsaturated Tb3+ cations because of the dissociation of solvents. Owning to the Lewis acid–base synergistic effect derived from open metal sites, free oxygen atoms and amino groups in the confined pore environments, SLU-1 with the aid of co-catalyst n-Bu4NBr exhibited high catalytic activity on the cycloaddition of CO2 with epoxides and under mild solvent-free conditions, especially for epoxides with smaller size. A highly robust microporous framework of {(Me2NH2)4[Tb4(DDAC)3(HCO2)(OH2)2]⋅6DMF⋅5H2O}n (SLU-1) with hierarchical channels and cage-like voids exhibits the high catalytic activity on the cycloaddition reaction of CO2 with epoxides and under mild solvent-free condition. [ABSTRACT FROM AUTHOR]