“…Although many interesting coordination polymeric frameworks are constructed by rational selection of multi-dentate bridging organic ligand as "spacer" and the metal ion or multi-core metal cluster as "node" [6][7][8] , much attention has been paid to the assembly of mixed 3d transition metals (TM) [9,10] , while the 3d-4f heterometallic polymers have received less attention [11][12][13][14][15][16] , mainly because the competitive reactions between 3d and 4f metals chelated to the same ligand often lead to homometallic polymers rather than heterometallic ones. Recently, we have explored the synthesis of the 3d-4f heterometallic polymers, and successfully obtained a series of 3-D Ln-TM wheel cluster polymers [Er 7 (μ 3 -O)(μ 3 -OH) 6 (bdc) 3 ](ina) 9 [Cu 3 X 4 ] (X = Cl or Br, H 2 bdc=1,2-benzenedicarboxylic acid, Hina = isonicotinic acid) [12] and [Ln 6 (μ 3 -O) 2 ](IN) 18 [Cu 8 (μ 4 -I) 2 -(μ 2 -I) 3 ]·H 3 O (HIN = isonicotinate acid ; Ln = Y, Nd, Dy, Gd, Sm, Eu, Tb) [13] , 3-D Ln-TM nanosized hydroxo-Ln cluster polymers [Ln 14 (μ 6 -O)(μ 3 -OH) 20 [14] , and 3-D Ln-TM pillared-layer polymers Ln 2 (bdc) 2 (ina) 2 (H 2 O) 2 Cu·X (H 2 bdc = 1,2-benzenedicarboxylic acid; Ln = Eu, Sm, Nd, X = ClO 4 ; Ln = Nd, X = Cl ) [15] , Ln 2 Cu 7 I 6 (ina) 7 -(H 2 O) 6 ·H 2 O (Ln = Ce, Sm) and Er 4 (OH) 4 Cu 5 I 4 (ina) 6 (na)-(2,5-pdc)·0.3H 2 O (Hna = nicotinic acid, 2,5-H 2 pdc = 2,5-pyridinedicar-boxylic acid) [16] . The structures of these 3-D Ln-TM polymers are based on multi-core metal cluster as "node" and bridging organic ligand with pyridine functional group as "spacer".…”