Conversion from Heterometallic to Homometallic Metal‐Organic Frameworks

Two new heterometallic metal-organic frameworks (MOFs), LnZnTPO 1 and 2 , and two homometallic MOFs, LnTPO 3 and 4 (Ln = Eu for 1 and 3 , and Tb for 2 and 4 ; H 3 TPO = tris-(4-carboxyphenyl)phosphine oxide) were synthesized, and their structures and properties were analyzed. They were prepared by solvothermal reaction of the C 3 -symmetric ligand H 3 TPO with the corresponding metal ion(s) (a mixture of Ln 3+ and Zn 2+ for 1 and 2 , and Ln 3+ alone for 3 and 4 ). Single-crystal X-ray diffraction (SXRD) analysis revealed that 1 and 3 are isostructural to 2 and 4 , respectively. Thermogravimetric analysis (TGA) showed that the framework is thermally stable up to about 400 degrees C for 1 and 2 , and about 450 degrees C for 3 and 4 . Powder X-ray diffraction (PXRD) analysis showed their pore structure changes during drying processes. The shapes of gas sorption isotherms for 1 and 3 are almost identical to those for 2 and 4 , respectively. Solvothermal immersion of 1 and 2 in Tb 3+ and Eu 3+ solutions resulted in the framework metal-ion exchange affording 4 and 3 , respectively, as confirmed by photoluminescence (PL), PXRD, infrared (IR), and inductively coupled plasma atomic emission spectroscopy (ICP-AES) analyses.