Exploring the Role of Functional Groups in Modulating NO and CO Adsorption and Diffusion in 2D (Zn)MOF-470: A Multiscale Computational Study

This investigation employed a multiscale computational approach, comprising density functional theory (DFT) and MP2 methods for the first-principles aspect and GCMC and molecular dynamics (MD) techniques for the molecular simulation aspect. The impact of functionalizing the organic linker of the metal–organic framework (MOF) structure with –NH2, –NO2, −OH, and –SH on nitric oxide (NO) and carbon monoxide (CO) adsorption and diffusion was also investigated. The adsorption sites of the NO and CO molecules on various organic and metal models were investigated. According to DFT calculations, the −NH2 functional group exhibits the strongest binding with NO, while the −OH functional group has the strongest binding with CO, with corresponding energies of −4.618 and −4.031 kcal·mol–1. The findings indicate that NO molecules undergo di-, tri-, and tetramerization on the metal cluster, which is not observed with the CO molecules. The uptake of NO from GCMC simulations changes with functional groups, with quantities of 189.69 (25.39), 186.06 (24.9), 153.33 (20.53), and 142.88 (19.13) cm3·g–1 (wt %), respectively. The uptake of CO varies with functional groups, with the levels of 116.19 (14.5), 109.9 (13.73), 108.91 (13.61), and 102.16 (12.76) cm3·g–1 (wt %), respectively. The results of MD simulations showed that adding functional groups has caused a further decrease in the movement of NO compared to that of CO. In general, the presence of water molecules leads to a reduction in the movement of adsorbed molecules. Moreover, the mobility of NO molecules within the X-(Zn)MOF-470 structures varies among different environments. However, CO molecules diffuse in an anisotropic manner. There is a strong relationship between the addition of functional groups and the reduction of diffusion coefficients of NO and CO molecules, and this reduction is greater for NO molecules than for CO. The outcomes of the simulations demonstrate that modifying (Zn)MOF-470 with functional groups can offer potential benefits in terms of increasing its storage capacity and decreasing the release of NO and CO signaling molecules. As such, the potential of (Zn)MOF-470 and its functionalization in the field of drug delivery are promising avenues for further research.