Magnetic and magnetocaloric properties of the two-dimensional Ln2(phthalate)3(H2O) (Ln = Gd-Dy) framework series

• The magnetic properties of the Ln 2 (phthalate) 3 (H 2 O) (Ln = Gd, Tb and Dy) were explored. • The Gd analogue has the best performance as a magnetocaloric, which unusually for Gd is maximised at 4 K rather than below 2 K. • This is attributed to the stronger interactions in this compounds being stronger than other members of the series. • This highlights a route forward to developing more sustainable magnetocalorics for replacing cooling using liquid He. The magnetic properties of a series of layered, two-dimensional Ln 2 (phth) 3 (H 2 O) materials (where Ln = Gd-Dy and phth = phthalate) metal–organic framework (MOF) materials have been examined to evaluate their potential as magnetocaloric materials. The Gd 2 (phth) 3 (H 2 O) material was found to exhibit the best performance of the series with a −Δ S m max of 16.3 J kg −1 K −1 for a magnetic field change of 5–0 T. Although modest compared to other Gd-based magnetocaloric frameworks, this material was notable for exhibiting its peak entropy change at 4 K. This contrasts with the majority of Gd-based magnetocaloric materials whose performance is usually optimised at 2 K (or lower) and found to rapidly decrease with increasing temperature and is attributed to the stronger magnetic interactions present in this material.