Construction of Chimeric Metal-Organic Frameworks with Symmetry-Mismatched Building Blocks

Abstract

Chimeric metal-organic frameworks (CMOFs) composedof symmetry-mismatchedinorganic and organic building blocks are rare because the interconnectionsbetween these blocks are topologically demanding. Herein, an MOF withsymmetry-matched building blocks is used as a self-template for thetemplate-assisted synthesis of CMOFs. Specifically, the post-synthetictransformation of the [Zn4O(COO)(6)] clustersin the self-templating MOF into the [Fe-3 O-III(COO)(6)](+) clusters with symmetry-mismatched trigonal prismaticsite symmetry affords isoreticular CMOFs while maintaining the templatemorphology and crystallinity. The framework strain of CMOFs due tothe symmetry-mismatched linkages between their building blocks isreduced by modulating the conformation of organic building blockswith torsional degrees of freedom. The further transformation of [Fe-3 O-III(COO)(6)](+)-based CMOFsthrough redox-facilitated metal exchange using Cr2+ ionsyields highly stable isostructural CMOFs containing [Cr-3 O-III(COO)(6)](+) clusters and exhibitingstabilities in strongly acidic and moderately basic media comparableto those of prototypical [Cr-3 O-III(COO)(6)](+)-based MOFs with symmetry-matched building blocks. Theseresults hold significant potential and highlight the vast opportunitiesfor revisiting well-known yet fragile MOFs built upon the zinc acetateclusters.