From condensed lanthanide coordination solids to microporous frameworks having accessible metal sites

The combination of terbium nitrate and 1,4-benzenedicarboxylic acid (H2BDC) in the presence of triethylamine yields the compound Tb-2(BDC)(3).(H2O)(4) , which has an extended nonporous structure constructed from copolymerized BDC and To(III) units. The multidentate functionality of BDC and the tenden cy of Tb to have a high coordination number has allowed water to act as a t erminal ligand to Tb in the structure. Upon thermally liberating the water ligands, a microporous material, Tb-2(BDC)(3), is achieved, which has exten ded 1-D channels and the same framework structure as that of the as-synthes ized solid as evidenced by XRPD. Water sorption isotherm data proves that T b-2(BDC)(3) has permanent microporosity, and points to the presence of acce ssible metal sites within the pores, which also allows the sorption of ammo nia to give Tb-2(BDC)(3).(NH3)(4) Luminescence Lifetime measurements confir m that resorbed water and sorbed ammonia are bound to Tb and that they give distinctly different decay constants.