Structure of the Polymer Backbones in polyMOF Materials

Abstract

The molecular connectivity of polymer−metal−organic framework (polyMOF) hybrid materials was investigated using density functional theory calculations and solid-state NMR spectroscopy. The architectural constraints that dictate the formation of polyMOFs were assessed by examining poly(1,4-benzenedicarboxylic acid) (pbdc) polymers in two archetypical MOF lattices (UiO-66 and IRMOF-1). Modeling of the polyMOFs showed that in the IRMOF-1-type lattice, six, seven, and eight methylene (−CH 2 −) groups between 1,4-benzenedicarboxylate (terephthalate, bdc 2− ) units can be accommodated without significant distortions, while in the UiO-66type lattice, an optimal spacing of seven methylene groups between bdc 2− units is needed to minimize strain. Solid-state NMR supports these predictions and reveals pronounced spectral differences for the same polymer in the two polyMOF lattices. With seven methylene groups, polyUiO-66-7a shows 7 ± 3% of uncoordinated terephthalate linkers, while these are undetectable (<4%) in the corresponding polyIRMOF-1-7a. In addition, NMR-detected backbone mobility is significantly higher in the polyIRMOF-1-7a than in the corresponding polyUiO-66-7a, again indicative of taut chains in the latter.

Tethering Effects in Oligomer-Based Metal–Organic Frameworks

“…The alkyl chains in the linker oligomers appear to serve the same purpose in these syntheses by providing sufficient steric bulk to prohibit interpenetration. While IRMOF-1 analogues were synthesized in DMF in previous studies with both oligomeric , and polymeric , H 2 bdc, the ability of crosslinked MOF linkers to disfavor interpenetration is a heretofore unrecognized synthetic benefit.…”

Inside polyMOFs: layered structures in polymer-based metal–organic frameworks

“…This nding suggests that individual polymer chains extend throughout the material and that multiple polymer chains contribute to the binding at each SBU. 26 Indeed, layered spacings similar to these have been observed in assemblies of Zr-phosphonate and polyphenylmaleimide, 27 demonstrating the tendency for polymers to self-assemble into layers in the presence of layered metaloxides. However, this is the rst demonstration of such layered assemblies in polymer-MOF hybrid materials.…”

Tethering Flexible Polymers to Crystalline Porous Materials: A Win–Win Hybridization Approach

“…first solved the above challenge by Density Functional Theory (DFT) calculation and solid‐state nuclear magnetic resonance (ssNMR) analysis (Figure 7). [43] Their work not only proved the existence of polymer moieties in polyMOF structures but also guided the future design and preparation of functional polyMOFs toward practical applications.…”

“… (a,b) Illustration of the calculation of PolyIRMOF‐1‐7a and polyUiO‐66‐7a structure; (c) Probing for uncoordinated linkers and strain in polyMOFs with ‐(CH 2 ) 7 ‐ backbone spacer segments by multiCP 13 C NMR [43] . Copyright 2020, American Chemical Society.…”