Microwave-Assisted Synthesis of a Series of Lanthanide Metal–Organic Frameworks and Gas Sorption Properties

A series of isostructural microporous lanthanide metal–organic
frameworks (MOFs) formulated as [Ln2(TPO)2(HCOO)]·(Me2NH2)·(DMF)4·(H2O)6 {Ln = Y (1), Sm (2), Eu
(3), Gd (4), Tb (5), Dy (6), Ho (7), Er (8), Tm (9), Yb (10), and Lu (11); H3TPO
= tris-(4-carboxylphenyl)­phosphineoxide; DMF = N,N-dimethylformamide} has been synthesized under microwave-assisted
solvothermal reaction for 30 min. Alternatively, if a conventional
solvothermal reaction is carried out under the same temperature, a
much longer time (3 days) is needed for the same phase in similar
yield. Structure analysis reveals that the framework is a 4,8-connected
network with point symbol (410·616·82) (45·6)2, which is the subnet
of alb net. Thermal gravimetric analyses
performed on as-synthesized MOFs reveal that the frameworks have high
thermal stability. The luminescent properties of 2, 3, 5, and 6 were investigated and
show characteristic emissions for Sm­(III), Eu­(III), Tb­(III), and Dy­(III)
at room temperature, respectively. Gas sorption properties of 1 and 3 were studied by experimentally measuring
nitrogen, argon, carbon dioxide, methane, and hydrogen sorption isotherms.
The resulting materials show high and preferential CO2 adsorption
over N2 gas at ambient temperature, indicating that the
present materials can be applied in a CO2 capture process.