Two novel three-dimensional interpenetrated uranyl-organic frameworks, (NH4)(4)[(UO2)(4)(L-1)(3)] center dot 6H(2)O (1) and [(UO2)(2)(H2O)(2)L-2]center dot 2H(2)O (2), where L-1 = tetrakis(3-carboxyphenyl)silicon and L-2 = tetrakis(4-carbOxyphenyl)silicon, were synthesized by a combination of two isomeric tetrahedral silinon-centered ligands with 3-connected triangular [(UO2)(COO)(3)](-) and 4-connected dinuclear [(UO2)(2)(COO)(4) ] units, respectively. Structural analyses indicate that 1,possesses a 2-fold interpenetrating anion bor-network, while 2 exhibits a 3-fold interpenetrated 4,4-connected neutral network with pts topology. Both compounds were characterized by thermogravirrietric analysis and-IR, UV-vis, and photoluminescence spectroscopy. A relativistic density functional theory (DFT) investigation on 10 model compounds of 1 and 2 shows good agreement of the structural parameters, stretching vibrational frequencies, and absorption with experimental results; the time-dependent DFT calculations unravel that low-energy absorption bands originate from ligand-to-uranium charge transfer.