A Local Structure Analysis of Defects in UiO-66: Insights from Solid-State Nuclear Magnetic Resonance and X-ray Absorption Fine Structure
Jiabin Xu, Kun Feng, Wanli Zhang, Amrit Venkatesh, Ivan Hung, Yuzhen Liu, Jingyan Liu, Shu‐Ting Li, Giuliana Battiston, Zhehong Gan, Shoushun Chen, Yun Mui Yiu, Jun Zhong, Tsun‐Kong Sham, Yining Huang
Abstract
Defect engineering in metal–organic frameworks (MOFs) offers a promising approach to modify material properties by introducing controlled structural imperfections. Zr-based MOFs, particularly the well-known UiO-66, hold significant potential for diverse applications. Defects in UiO-66 can be generated using monocarboxylic acids as modulators, among other methods. However, resolving the atomic-level local structures of these defects remains a considerable challenge. In this study, the local structures of these defects are carefully characterized by multinuclear solid-state NMR spectroscopy (SSNMR) in combination with X-ray absorption fine structure (XAFS). In situ heating XAFS analyses at Zr K-edge reveal critical changes in the local structure of Zr during the removal of trifluoroacetic acid (TFA), including the decreased Zr–O coordination numbers and alterations in Zr–Zr bond distances. Multinuclear 1 H, 13 C, 19 F, 35/37 Cl, 17 O solid-state NMR methods are used to identify capping species and defect-associated species. Subsequently, the engineered defects are found to significantly improve the catalytic performance of Pt nanoparticles (NPs) integrated into the defective UiO-66 framework. Pt-UiO-66 with defects exhibits much improved hydrogen evolution reaction (HER) activity and stability compared to the Pt-UiO-66 without defects.