Microporous Metal−Organic Frameworks Built on a Ln₃ Cluster as a Six-Connecting Node

Two novel microporous metal−organic frameworks, {[Pr 3 (ATPT) 2 (HATPT) 4 ]·(NO 3 )·8H 2 O} n ( 1 ) and {[Nd 3 (ATPT) 3 (HATPT) 3 ]·9H 2 O} n ( 2 ) (H 2 ATPT = 2-aminoterephthalic acid), were synthesized by slow diffusion of aqueous solution of H 2 ATPT and Pr(NO 3 ) 3 ·6H 2 O or Nd(NO 3 ) 3 ·6H 2 O in 2-propanol. X-ray diffraction analyses reveal that their three-dimensional structures are composed of ATPT spacers and trinulcear lanthanide nodes, in which there are two crystallographically independent lanthanide atoms, nine- and twelve-coordinated. Twelve ATPT anions, adopting an unprecedented pentadentate η 1:η 1:η 1:η 2 bridging coordination mode, ligate the trinuclear node. Each pair of ATPT anions acts as a double bridge and is considered as one connection. Thus each trinuclear core is connected to the six nearest Ln 3 neighbors forming a NaCl-type crystal lattice with a three-dimensional intersecting channel system of ca. 1.3-nm spacing between the centers of the adjacent clusters. The guest water molecules located in the large cavities can be removed without ruining the microporous framework. Thermal gravimetric and powder X-ray diffraction analyses confirm that small molecules, four methanol molecules per Pr 3 unit and six methanol molecules per Nd 3 unit, respectively, can be absorbed into the dehydrated microporous frameworks.