Defects in metal-organic frameworks: a compromise between adsorption and stability?

TL;DR

This study investigates how defect engineering in zirconium-based UiO-66 metal-organic frameworks affects the balance between CO2 adsorption capacity and mechanical stability, highlighting defect types and heterogeneity as key factors.

Contribution

It provides a systematic analysis of defect scenarios in UiO-66, revealing how defect type and heterogeneity influence the trade-off between adsorption and stability.

Findings

High defect concentration enhances CO2 uptake but reduces mechanical stability.

Reo type defects and trifluoroacetate substitution mitigate stability loss.

Heterogeneity and auxeticity may help balance adsorption and stability.

Abstract

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.