(88b) Computational and Experimental Characterization of the Ligand Environment of a Ni-Oxo Catalyst Supported in Metal?Organic Framework NU-1000

Heterogeneous catalysts exhibit significant changes in composition under different operating conditions, and these compositional changes can have significant effects on catalytic performance. For bulk metal heterogeneous catalysts, relationships between composition and catalytic operating conditions are well documented. However, the influence of operating conditions on the compositions of ligated metal cation catalysts remains largely unresolved. To address this, we use a combination of density functional theory (DFT), first principles thermodynamics (FPT), and pair distribution function (PDF) analysis to investigate ligand environments present on a Ni₄O_xH_y cluster supported in the metal-organic framework NU-1000. Experimental PDFs provide insights into both the Ni-O coordination numbers and the Ni−O, Ni···Ni, and Ni···Zr distances, while DFT and FPT provide molecular level insights into the ligand environments that could result in the PDFs observed experimentally. A total of 854 ligand environments are investigated. Our findings suggest significant OH and H₂O content, and that different Ni ions within the cluster and/or NU-1000 structure may comprise subtly different numbers of these ligands. These insights will be useful for modeling catalysis on Ni oxo and other similar catalysts.