Two chelating-amino-functionalized lanthanide metal–organic frameworks, Er-DADQ and Eu-DADQ, were synthesized with a flexible dicarboxylate ligand based on quinoxaline (H₂DADQ = N,N′-dibenzoic acid-2,3-diaminoquinoxaline). N₂ adsorption indicates that they exhibit a stable microporous framework with a BET surface area of 136.78 m² g⁻¹. CO₂ adsorptions have also been studied at different temperatures. The amino groups in the MOFs enhanced the uptake of RhB with COOH groups. RhB–MO and RhB–CV separations have also been successfully conducted. The MOFs act as efficient Lewis acid catalysts for the cyanosilylation of aldehydes and ketones in high yields in a short reaction time due to the higher Lewis acidity and open sites of the metal ions after activation.