A thiol-containing zirconium MOF functionalized with silver nanoparticles for synergistic CO2 cycloaddition reactions

Thiol-containing biomolecules, such as cysteine and glutathione, play essential roles in regulating the polarity and reactivity of the systems. Among functional MOFs, thiol MOFs, a subclass with a thiol group-containing ligand, are relatively less explored due to their synthetic challenges and stability and storage issues. Despite these drawbacks, they have many advantages due to the electronically soft thiol groups with strong reactivity and affinity toward soft metal ions. Herein, we have taken advantage of the affinity between thiol groups and a soft metal (Ag) by functionalizing a thiol MOF with Ag ions and finally synthesizing a silver nanoparticle-functionalized heterogeneous catalyst (Ag@Zr-DMBD). The Zr,Ag centre of the thiol MOF catalyst acts as an active centre and synergistically binds with the electron-rich oxygen atom of a terminal epoxide for efficient CO2 fixation to the corresponding cyclic carbonates under atmospheric CO2 pressure in 8 h. Finally, a rationalized reaction mechanism is proposed based on literature reports and current results. This work presents a viable strategy for using thiol MOFs as heterogeneous catalysts for CO2 fixation under mild conditions.