SCSC Transformation of Heterobimetallic 2D MOF to Homometallic 2D MOF via Solvent-Assisted Removal of Second Metal Component: An Add-and-Remove Strategy

Abstract

Constructing high-dimensional metal–organic framework (MOF) materials that cannot be reached by direct methods is demanding. We herein report the construction of a two-dimensional (2D) copper(I) iodide MOF via an add-and-remove strategy of a second metal component (HgI₂). The networking reaction of an O₂S₂-macrocycle (L) with CuI via a bridging exocyclic coordination under the direct condition was unsatisfactory because of its one-dimensional (1D) product {[(μ₄-Cu₃I₃)(L)₂]·2CH₃CN·CH₂Cl₂}_n (1) with low yield. Alternatively, the self-assembly of L with a mixture of CuI and HgI₂ allows the generation of a 2D heterobimetallic Cu(I)/Hg(II)-MOF {[Cu₂(μ-Hg₂I₄)(L)₂(CH₃CN)₂I₂]·toluene}_n (2, brick wall) cross-linked by μ-Hg₂I₄ square dimers via the bridging exocoordination mode. When the crystals of 2 were immersed in methanol, the crystals were converted to a desired 2D Cu(I)-MOF [(μ₄-Cu₂I₂)(L)₂]_n (3, square grid) by the replacement of the cross-linker μ-Hg₂I₄ with μ₄-Cu₂I₂ via the solvent-assisted etching. Interestingly, this 2D–[1D]*–2D conversion process that proceeds in an SCSC mode is completed by the dimerization of open coordinating site CuI* to form a μ₄-Cu₂I₂ node (2CuI* → Cu₂I₂), preserving the 2D dimensionality. The conversion process is discussed based on PXRD, EDX, AFM, TGA, and NMR data.