A Gd-based borate-carbonate framework exhibiting a large magnetocaloric effect at a low magnetic field.

A 3D borate–carbonate framework, GdB(OH)4CO3 (1), was synthesized. Magnetic study reveals that its MCE is up to 33.5 J kg−1 K−1 at 2 K and 2 T, due to the introduction of a long magnetic exchange path of Gd–O–B–O–Gd leading to 1 exhibiting weak magnetic interaction.