Elucidating phase transformation of Eu-based metal organic framework with intermediate isolation and theoretical calculations

Self assembly between 2,5-difluoro-3,6-dimercaptoterephthalic acid (H 4 dfdmt ) and Eu( iii ) centers under solvothermal conditions gave a 3D reddish-brown metal-organic framework (MOF, Eu-dfdmt-RB ) that managed to transit to a 2D black analogue ( Eu-dfdmt-B ) by extending the reaction time. The putative intermediate ( dfdmt-INT ) for this transformation was isolated and crystallographically characterized. Theoretical calculation shows that Eu-dfdmt-RB is thermodynamically less stable than Eu-dfdmt-B and hence dissolutes to form dfdmt-INT , which finally repreciptates as Eu-dfdmt-B with an extended reaction time. Phase transformation from Eu-dfdmt-RB to Eu-dfdmt-B was rationalized as a dissolution-reprecipitation process with dfdmt-INT isolated as the key intermediate.