A Series of 3D Rare‐Earth‐Metal–Organic Frameworks with Isolated Guest Keggin Silicotungstate Fragments as Anion Templates

Six rare‐earth (RE) metal constructed 3D metal–organic frameworks, [RE(pydc)(H 2 O) n ] 4 [SiW 12 O 40 ] · 4H 2 O [RE = Tm III ( 1 ), Y III ( 2 ), Pr III ( 3 ), La III ( 4 ), Sm III ( 5 ), Eu III ( 6 ); n = 3 ( 1 , 2 ), 4 ( 3 – 6 ); H 2 pydc = pyridine‐2,6‐dicarboxylic acid], have been synthesized and characterized by elemental analyses, inductively coupled plasma techniques, IR and UV spectroscopy, thermogravimetric analyses (for 1 and 3 ), X‐ray powder diffraction, and single‐crystal X‐ray diffraction. The structural analyses indicate that 1 – 6 are basically isostructural and show a rare host 3D framework that contains [SiW 12 O 40 ] 4– Keggin polyoxoanions as templates. Photoluminescence measurements reveal that 1 – 5 show the luminescence of pydc ligands, whereas 6 displays a unique red luminescence.