Surface Modification Strategy for Enhanced NO 2 Capture in Metal-Organic Frameworks.

The interaction strength of nitrogen dioxide (NO 2 ) with a set of 43 functionalized benzene molecules was investigated by performing density functional theory (DFT) calculations. The functional groups under study were strategically selected as potential modifications of the organic linker of existing metal-organic frameworks (MOFs) in order to enhance their uptake of NO 2 molecules. Among the functional groups considered, the highest interaction energy with NO 2 (5.4 kcal/mol) was found for phenyl hydrogen sulfate (-OSO 3 H) at the RI-DSD-BLYP/def2-TZVPP level of theory-an interaction almost three times larger than the corresponding binding energy for non-functionalized benzene (2.0 kcal/mol). The groups with the strongest NO 2 interactions (-OSO 3 H, -PO 3 H 2 , -OPO 3 H 2 ) were selected for functionalizing the linker of IRMOF-8 and investigating the trend in their NO 2 uptake capacities with grand canonical Monte Carlo (GCMC) simulations at ambient temperature for a wide pressure range. The predicted isotherms show a profound enhancement of the NO 2 uptake with the introduction of the strongly-binding functional groups in the framework, rendering them promising modification candidates for improving the NO 2 uptake performance not only in MOFs but also in various other porous materials.