Implementation of a Core-Shell Design Approach for Constructing MOFs for CO Capture.

Adsorption-based capture of CO from flue gas and from air requires materials that have a high affinity for CO and can resist water molecules that competitively bind to adsorption sites. Here, we present a core-shell metal-organic framework (MOF) design strategy where the core MOF is designed to selectively adsorb CO, and the shell MOF is designed to block HO diffusion into the core. To implement and test this strategy, we used the zirconium (Zr)-based UiO MOF platform because of its relative structural rigidity and chemical stability. Previously reported computational screening results were used to select optimal core and shell MOF compositions from a basis set of possible building blocks, and the target core-shell MOFs were prepared. Their compositions and structures were characterized using scanning electron microscopy, transmission electron microscopy, and powder X-ray diffraction. Multigas (CO, N, and HO) sorption data were collected both for the core-shell MOFs and for the core and shell MOFs individually. These data were compared to determine whether the core-shell MOF architecture improved the CO capture performance under humid conditions. The combination of experimental and computational results demonstrated that adding a shell layer with high CO/HO diffusion selectivity can significantly reduce the effect of water on CO uptake.