Constructing stable uranyl-copper(II) bimetallic organic frameworks using rigid thiophenedicarboxylic acid.

Through the incorporation of Cu(II) ions as additional connecting nodes to form heterometallic uranyl-organic frameworks with rigid ligands, we have successfully synthesized three extended complexes with varying dimensions. Notably, complex 1 features a robust 3D cds net structure and demonstrates exceptional thermal stability above 250 °C. [Display omitted] By introducing Cu(II) ions as additional connecting nodes to construct stable heterometallic uranyl-organic frameworks (UOFs) with thiophene-2,5-dicarboxylic acid (H 2 TDC) and N -donor auxiliary ligands, three new uranyl complexes, namely, [Cu(phen)(UO 2)(TDC) 2 ] (1), [Cu(phen-NO 2) 2 (UO 2)(TDC) 2 ]·3H 2 O (2), and [Cu(phen-NH 2)(H 2 O) 2 (UO 2)(TDC) 2 ]·4H 2 O (3) (phen = 1,10-phenanthroline) have been successfully synthesized by hydrothermal reaction. Complex 1 exhibits a rare three-dimensional (3D) network structure of cds topology connected by UO 2 , Cu(phen), and TDC units. Both complexes 2 and 3 feature similar one-dimensional chain structures based on UO 2 , TDC, Cu(Phen-NO 2) 2 and UO 2 , TDC, Cu(phen-NH 2)(H 2 O) 2 respectively. The N -donor auxiliary ligands play a key role in determining their structural dimensionalities and bandgaps formation. Among the three uranyl complexes, phen with a smaller size than its derivatives, phen-NO 2 and phen-NH 2 , was found to be favorable for constructing 3D UOFs. Moreover, complexes with both phen-NO 2 and phen-NH 2 showed varying degrees of redshift on optical spectra. The UV–Visible diffuse-reflectance spectra, analyzed with Tauc's fitting in considering Urbach tailing, revealed an indirect bandgap of 2.94 eV, an indirect bandgap of 2.67 eV, and a direct bandgap of 2.45 eV for 1 , 2 and 3 , respectively. Moreover, thermogravimetric analyses indicate that 3D anhydrous uranyl complex 1 possessed a robust structure and excellent thermal stability above 250 ℃. [ABSTRACT FROM AUTHOR]