Enhancing CO adsorption capacity of ZIF-8 by synergetic effect of high pressure and temperature.

Metal-organic frameworks (MOFs) and zeolitic imidazolate frameworks (ZIFs) are promising porous materials for adsorption and storage of greenhouse gases, especially CO. In this study, guided by the CO phase diagram, we explore the adsorption behavior of solid CO loaded with ZIF-8 framework by heating the sample under high pressures, resulting in a drastic improvement in the CO uptake. The behavior of CO under simultaneous high temperature (T) and pressure (P) conditions is directly monitored by in situ FTIR spectroscopy. The remarkable enhancement in CO adsorption capability observed can be attributed to the synergetic effect of high T and P: high temperature greatly enhances the transport property of solid CO by facilitating its diffusion into the framework; high pressure effectively modifies the pore size and shape via changing the linker orientation and creating new adsorption sites within ZIF-8. Our study thus provides important new insights into the tunability and enhancement of CO adsorptive capability in MOFs/ZIFs using pressure and temperature combined as a synergetic approach.