Abstract
Metal-organic frameworks (MOFs) and zeolitic imidazolate frameworks (ZIFs) are promising porous materials for adsorption and storage of greenhouse gases, especially CO2. In this study, guided by the CO2 phase diagram, we explore the adsorption behavior of solid CO2 loaded with ZIF-8 framework by heating the sample under high pressures, resulting in a drastic improvement in the CO2 uptake. The behavior of CO2 under simultaneous high temperature (T) and pressure (P) conditions is directly monitored by in situ FTIR spectroscopy. The remarkable enhancement in CO2 adsorption capability observed can be attributed to the synergetic effect of high T and P: high temperature greatly enhances the transport property of solid CO2 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 CO2 adsorptive capability in MOFs/ZIFs using pressure and temperature combined as a synergetic approach.