Spatio‐Chemical Heterogeneity of Defect‐Engineered Metal–Organic Framework Crystals Revealed by Full‐Field Tomographic X‐ray Absorption Spectroscopy
Darío Ferreira Sánchez, Johannes Ihli, Damin Zhang, Thomas Rohrbach, P. Zimmermann, Jinhee Lee, Camelia N. Borca, Natascha Böhlen, Daniel Grolimund, Jeroen A. van Bokhoven, Marco Ranocchiari
Abstract
The introduction of structural defects in metal-organic frameworks (MOFs), often achieved through the fractional use of defective linkers, is emerging as a means to refine the properties of existing MOFs. These linkers, missing coordination fragments, create unsaturated framework nodes that may alter the properties of the MOF. A property-targeted utilization of this approach demands an understanding of the structure of the defect-engineered MOF. We demonstrate that full-field X-ray absorption near-edge structure computed tomography can help to improve our understanding. This was demonstrated by visualizing the chemical heterogeneity found in defect-engineered HKUST-1 MOF crystals. A non-uniform incorporation and zonation of the defective linker was discovered, leading to the presence of clusters of a second coordination polymer within HKUST-1. The former is suggested to be responsible, in part, for altered MOF properties; thereby, advocating for a spatio-chemically resolved characterization of MOFs.