Host–guest adsorption energetics in functionalized UiO-66 nanocrystals for selective VOC sensing

Abstract

Volatile organic compounds (VOCs), such as formaldehyde (HCHO) and acetone (C₃H₆O), are ubiquitous air pollutants in industrial and indoor environments and pose serious risks to human health, driving demand for selective, sensitive detection. Metal–organic frameworks (MOFs) are promising sensing nanomaterials due to their structural tunability and modifiable pore chemistry. However, the vast structural diversity of MOFs makes it difficult to identify materials with selective responses toward specific VOCs, and current development still relies heavily on empirical trial-and-error screening. Herein, we integrate density functional theory (DFT) calculations, quartz crystal microbalance (QCM) experiments and complementary spectroscopic characterization to establish a rational design strategy for VOC-selective MOF sensors, using functionalized UiO-66 as a model. DFT analyses quantify adsorption energies, hydrogen-bonding interactions, dipole coupling, and electronic perturbations between functionalized UiO-66 and HCHO or C₃H₆O. QCM measurements, Fourier-transform infrared (FTIR) and UV-vis spectroscopy verify the theoretical predictions. Our results indicate that UiO-66-NH₂ preferentially responds to HCHO, while UiO-66-OH prefers C₃H₆O. This work shows a direct mechanistic link between the MOF structure and sensing performance, bypassing exhaustive empirical screening and laying a foundation for rational MOF sensor design.