S1 Supporting Information Single-Site Organozirconium Catalyst Embedded in a Metal–Organic Framework Rachel C. Klet, † Samat Tussupbayev, ‡ Joshua Borycz, ‡ James R. Gallagher, § Madelyn M. Stalzer, † Jeffrey T. Miller, §,⊥ Laura Gagliardi, ‡, * Joseph T. Hupp, †, * Tobin J. Marks, †, * Christopher J. Cramer, ‡, * Massimiliano Delferro, †, * Omar K. Farha †,||, * †Department of Chemistry, Northwestern University, Evanston, IL 60208, United States ‡Department of Chemistry, Supercomputing Institute, and Chemical Theory Center, University of Minnesota, Minneapolis, MN 55455, United States §Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL 60439 ⊥School of Chemical Engineering, Purdue University, W. Lafayette, IN 47907 ||Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia Table of Contents Materials and Methods S2 Instrumentation S2 Synthesis of Hf-NU-1000-ZrBn S3 ICP–AES Analysis S3 SEM–EDX of Hf-NU-1000-ZrBn S4 DRIFTS of Hf-NU-1000 and Hf-NU-1000-ZrBn S4 PXRD Pattern of Hf-NU-1000-ZrBn S5 N 2 Adsorption Isotherm Analysis S6 13 C SS NMR of Hf-NU-1000-ZrBn S7 1 H SS NMR of Hf-NU-1000-ZrBn S7 X-ray Absorption Spectroscopy Measurements and Analysis S8 Computational Details S12 Computational Study of Reaction of ZrBn 4 with Hf-NU-1000 S13 1-Hexene Polymerization with Hf-NU-1000-ZrBn S22 1 H and 13 C NMR of poly(1-hexene) S22 Polymerization Data for Poly(1-hexene) and Polyethylene S23 SEM Images of MOF Crystallites After Polymerization S24 PXRD Pattern of Hf-NU-1000-ZrBn After Polymerization S26 Ethylene Polymerization with Hf-NU-1000-ZrBn S27 1 H and 13 C NMR of polyethylene S28 DSC trace and FT-IR spectrum of polyethylene S29 Computational Study of Polymerization Mechanism and Selectivity S30 References S33