Conversion from Heterometallic to Homometallic Metal-Organic Frameworks

Abstract

Two new heterometallic metal-organic frameworks (MOFs), LnZnTPO1and2, and two homometallic MOFs, LnTPO3and4(Ln=Eu for1and3, and Tb for2and4; H3TPO=tris(4-carboxyphenyl)phosphine oxide) were synthesized, and their structures and properties were analyzed. They were prepared by solvothermal reaction of theC(3)-symmetric ligand H3TPO with the corresponding metal ion(s) (a mixture of Ln(3+)and Zn(2+)for1and2, and Ln(3+)alone for3and4). Single-crystal XRD (SXRD) analysis revealed that1and3are isostructural to2and4, respectively. TGA showed that the framework is thermally stable up to about 400 degrees C for1and2, and about 450 degrees C for3and4. PXRD analysis showed their pore-structure distortions without noticeable framework-structure changes during drying processes. The shapes of gas sorption isotherms for1and3are almost identical to those for2and4, respectively. Solvothermal immersion of1and2in Tb(3+)and Eu(3+)solutions resulted in the framework metal-ion exchange affording4and3, respectively, as confirmed by photoluminescence (PL), PXRD, IR, inductively coupled plasma atomic emission spectroscopy (ICP-AES), and energy-dispersive X-ray (EDX) analyses.