A Bumper Crop of Boiling-Water-Stable Metal–Organic Frameworks from Controlled Linker Sulfuration

Abstract

The series of highly stable porous solids here feature systematic, regiospecific sulfur substitutions on the organic linkers for versatile functions. One major surprise lies in the controllable sequential reactions between sodium thiomethoxide (NaSMe) and octafluorobiphenyl-4,4′-dicarboxylic acid (H 2 bpdc-8F; this was readily made without precious metal catalysts). Namely, 3, 4, 6, and 8 methylthio-substitutions can be respectively achieved with regiospecificity (i.e., to produce the four molecules H 2 bpdc-3S5F, H 2 bpdc-4S4F, H 2 bpdc-6S2F, H 2 bpdc-8MS). A second surprise lies in their persistent formation of the UiO-67type net with Zr(IV) ions, e.g., even in the case of the fully sulfurated H 2 bpdc-8MS. In addition to the remarkable breadth of functional control, all the Zr(IV)-based crystalline solids here are stable in boiling water (e.g., for 24 h) and in air as solventless, activated porous solids. Moreover, the thioether groups allow for convenient H 2 O 2 oxidation to fine-tune the hydrophilicity and luminescence properties and improve proton conductivity.Article pubs.acs.org/IC

Linker Deficiency, Aromatic Ring Fusion, and Electrocatalysis in a Porous Ni8-Pyrazolate Network

“…The 12-connected Ni 8 O 6 node can be considered topologically equivalent to the Zr 6 O 4 (OH) 4 12+ unit (e.g., as in the UiO series), which features a Zr 6 octahedron and an O 2– or OH – species on its 8 faces. One difference, however, is noted: while Ni 8 -pyrazolate nets reported so far uniformly feature full linker occupancy (i.e., one Ni 8 O 6 node per six ditopic linkers to give the 12 connections), the Zr 6 O 4 (OH) 4 unit was often found to fall short of the full 12 connections, ,− e.g., with the missing linkers filled in by monotopic formate/acetate or OH – /H 2 O ligands. Another difference lies in the softer Ni­(II)-pyrazolate pair (relative to Zr 4+ -carboxylate), which imparts more covalency and stability to the bonding, making the resultant framework less prone to deformation and degradation.…”

Proton conductive Zr-based MOFs

“…He and co-workers obtained four boiling-waterstable modified UiO-67-based MOFs, Zr-bpdc-3S5F, Zr-bpdc-4S4F, Zr-bpdc-6S2F and Zr-bpdc-8MS through solvothermal synthesis with a systematic region-specific sulfur substituent (Scheme 2) and ZrCl 4 as starting materials. 66 Among them, a single crystal appropriate for X-ray diffraction for Zr-bpdc-4S4F is acquired. The framework of Zr-bpdc-4S4F is basically the Scheme 2 The organic linkages appearing in the UiO-67 series MOFs.…”

“…Unsaturated fatty acid-based Zr-MOF. In 2018, by employing ZrOCl 2 •8H 2 O and fumaric acid (H 2 fum), X. M. Ren's group prepared a three-dimensional MOF MOF-801 in the light of a literature method, 66 and explored its stability, proton conductivity and application in composite films and fuel cells. 77 The crystal structure of the compound is simply described as follows: each Zr-oxide SBU containing six Zr 4+ atoms bridged by eight μ 3 -O atoms (four OH units and four O 2− anions) are joined by linear and ditopic fumarate bridges to constitute a three-dimensional framework having porous tetrahedral and octahedral cages.…”

A Structural Survey of Poly-Functional Dithiocarbamate Ligands and the Aggregation Patterns They Sustain

“…In the intra-cellular environment, glutathione (GSH), which is present in a higher concentration than in extra-cellular surroundings, reduces the disulphide bond to release 6-MPH in a GSH-responsive drug-delivery strategy that results in a 3-fold efficacy of the drug [21]. In other zirconium-based MOFs, regiospecific and modular substitution in the organic staves of the framework by (thio-ether) sulphur resulted in the formation of boiling water-insensitive materials that could be subjected to controlled, post-synthetic oxidation by hydrogen peroxide [22]; it is noted that (thiophene-)sulphur can play related roles for oxygen reduction in covalent organic frameworks [23]. In one final example highlighting the potential utility of sulphur-modified MOFs, recently, thio-functionalised MOFs have been shown to be effective in bioremediation.…”