Effect of Benzoic Acid as a Modulator in the Structure of UiO-66: An Experimental and Computational Study

The identification and quantification of defects are undoubtedly thorough challenges in the characterization of "defect-engineered" metal–organic frameworks (MOFs). UiO-66, known for its exceptional stability and defect tolerance, has been a popular target for defect-engineering studies. Herein, we show that synthesizing UiO-66 in the presence of an excess of benzoic acid is a reliable method for obtaining UiO-66 samples with a very high concentration of missing-cluster defects, allowing one to modulate specific properties (i.e., surface area and hydrophobicity). This was elucidated by a multitechnique marriage of experimental and computational methods: a combination of PXRD, dissolution/1H NMR spectroscopy, and N2 sorption measurements was used to quantify the defect loading, while vibrational spectroscopies (FTIR and Raman) allowed us to unequivocally identify the defect structure by comparison with DFT-simulated spectra and visual analysis of the computed vibrational modes.