  Defect engineering has arisen as a promising approach to tune and optimise
the adsorptive performance of metal-organic frameworks. However, the balance
between enhanced adsorption and structural stability remains an open question.
Here both CO2 adsorption capacity and mechanical stability are calculated for
the zirconium-based UiO-66, which is subject to systematic variations of defect
scenarios. Modulator-dependence, defect concentration and heterogeneity are
explored in isolation. Mechanical stability is shown to be compromised at high
pressures where uptake is enhanced with an increase in defect concentration.
Nonetheless this reduction in stability is minimised for reo type defects and
defects with trifluoroacetate substitution. Finally, heterogeneity and
auxeticity may also play a role in overcoming the compromise between adsorption
and stability.
