Two new metal–organic frameworks (MOFs), namely [Mn3(atpa)3(dmf)2] and [Mn2(tpa)2(dmf)2], were prepared in N,N‐dimethylformamide (dmf) from manganese(II) nitrate and two dicarboxylic acid ligands, 2‐aminoterephthalic acid (H2atpa) and terephthalic acid (H2tpa). The molecular structures of these MOFs are compared to two related coordination polymers, namely [Mn3(atpa)2(Hatpa)2] and [Mn3(tpa)3(def)2], which were obtained in N,N‐diethylformamide (def), to examine the effect of slight ligand or solvent changes on the framework architecture. The four Mn‐based MOFs were used as effective Lewis catalysts for the cyanosilylation of acetaldehyde. The four heterogeneous catalytic systems can be re‐used without any apparent loss of activity.