A heterometallic strategy to achieve a large magnetocaloric effect in polymeric 3d complexes

Metal formate frameworks [A][CrMn(HCOO)6] (A = CH3NH2CH3+ for 1 and CH3NH3+ for 2) with a large MCE were obtained, directed by the heterometallic strategy in which very weak magnetic interactions were achieved. A switch from antiferromagnetism to ferromagnetism occurs when replacing the CH3NH2CH3+ cation with CH3NH3+. The magnetic entropy change (−ΔSm) reached 48.20 J kg−1 K−1 for 2, which is the largest among the known polymeric 3d complexes.