Enhancing cis-trans azobenzene photoisomerization in mismatching mixed-linker multivariate Zr6 MOFs.

Multivariate metal-organic frameworks (MTV MOFs) have emerged as promising materials due to their ability to combine properties that enhance features beyond those of their pristine counterparts. Despite the potential for tailoring electronic properties through structural distortions and defect sites introduced by linkers of variable lengths, examples remain scarce, and information on the electronic structure of mismatching MTV MOFs is limited. Here, we present the multivariate mismatching linker approach to generate well-dispersed nanoparticulated MOFs with variable lattice parameters and porosity features controlled by mixed-linker composition. Structural defects, such as tangling linkers, are generated due to mismatching crystal lattices, tuning the electronic structure even at low concentrations. Combining biphenyl and azobenzene ditopic linkers in Zr6-MOFs promotes cis-trans photoisomerization of tangling azobenzene linkers, which is typically constrained in azobenzene MOFs with linkers bonded through both carboxylates. Moreover, introducing low quantities of azobenzene drastically reduces the bandgap of the materials due to the contribution of the azo group, which is supported by first-principles calculations. This paves the way for new photo-responsive materials for photo-switching applications.