Experimental and Theoretical Study on the Interchange between Zr and Ti within the MIL-125-NH₂ Metal Cluster

This study aims to investigate the effect of replacing Ti with Zr in the SBU of MIL-125-NH₂. We were able to replace Ti with Zr in the mixed metal synthesis of MIL-125-NH₂, for the first time. After experimentally confirming the consistency in their framework structure and comparing their morphology, we related the femtosecond light dynamics with photocatalytic CO₂ visible light conversion yield of the different variants in order to establish the composition-function relation in MIL-125 vis a vis CO₂ reduction. Introducing Zr to the system was found to cause structure defects due to missing linkers. The lifetime of the charge carriers for the mixed metal samples were shorter than that of the MIL-125-NH₂. The study of CO₂ photocatalytic reduction under visible light indicated that the NH₂ group enhances the photocatalytic activity while the Zr incorporation inside the MIL framework introduces no significant improvements. In addition, the material systems were modelled and simulated through DFT calculations which concluded that the decrease of the photocatalytic activity is not related to the system electronic structure, insinuating that defects are the culprit.