Self-Assembly of Lanthanide-Aluminum Cluster-Organic Frameworks with Magnetocaloric Effect and Luminescence.

The self-assembly of the lanthanide metal-organic frameworks presents a formidable challenge but profound significance. Compared with the metal-organic frameworks based on 4f-3d ions, the chemistry of 4f-3p metal-organic frameworks has not been fully explored so far. In this study, two lanthanide-aluminum-based clusters [Ln 6 Al(IN) 10 (μ 3 -OH) 5 (μ 3 -O) 3 (H 2 O) 8 ]· x H 2 O ( x = 2, Ln = Gd, abbreviated as Gd 6 Al ; x = 2.5, Ln = Eu, abbreviated as Eu 6 Al ; HIN = isonicotinic acid) have been meticulously designed and obtained by hydrothermal reaction at low pH. The crystallographic study revealed that both Gd 6 Al and Eu 6 Al clusters exhibit an unprecedented sandwiched metal-organic framework holding a highly ordered honeycomb network. To our knowledge, it is the first case of Ln-Al-based cluster-organic frameworks. Furthermore, magnetic investigation of Gd 6 Al manifests a decent magnetic entropy change of -Δ S m max = 28.8 J kg -1 K -1 at 2 K for Δ H = 7.0 T. Significantly, the introduction of Al III ions into the lanthanide metal-organic frameworks displays excellent solid-state luminescent capability with a lifetime of 371.6 μs and quantum yield of 6.64%. The construction and investigation of these two Ln-Al clusters represent great progress in the 4f-3p metal-organic framework.