Metal-organic frameworks (MOFs) provide an ideal platform for the assembly of chromophores and thus show wide potential applications in optoelectronic devices. The spatial arrangement and interaction of the incorporated chromophores play a key role in the generation of coherent optical and electronic properties. In this work, two series of benzo-(1,2;3,4;5,6)-tristhiophene (BTT) based Ln-MOFs (Ln-1s and Ln-2s) were synthesized. These two series of MOFs present different assembly states of BTT chromophores, that is, BTT-containing ligands exist as separated monomers in Ln-1s but gather as dimers in Ln-2s. From the comparison between these two series of MOFs and theoretical calculations, we show for the first time that this chromophore assembly state difference could affect the crystallization selectivity of MOFs towards different Ln3+ ions. In addition, the interaction between BTT chromophores in the dimer also leads to the red-shifted photoluminescence and enhanced photocurrent of Ln-2s relative to those of Ln-1s. The results of this work demonstrate the multiple functions of interchromophoric interactions in the structures and optoelectronic properties of MOFs.