Dense Dithiolene Units on Metal–Organic Frameworks for Mercury Removal and Superprotonic Conduction

Abstract

With 2-COOH and 4-SH donors all packed onto the benzene ring, tetrasulfanyl terephthalic acid (TST) is a simple yet fully equipped ligand to move the field of metal-coordination materialsit is now accomplished. The hard-soft carboxyl-thiol synergy is leveraged here in selectively bonding the carboxyl units to Zr­(IV) ions to form the same cubic net of UiO-66 (this being based on the terephthalic linker)with the free-standing dithiolene units equipping the grid of ZrTST. The 3D network of ZrTST averages about 7.6 connections [as in Zr6O4(OH)4(C8H4O4S4)3.8], with the other 4.4 sealed by acetate ions. The ZrTST solid is stable in boiling water (it is formed in water/acetic acid/ethane dithiol) and remains ordered even above 300 °C. The thiol-enabled ZrTST (powder) takes up mercury from water with a high distribution coefficient K d (e.g., 1.2 × 106 mL·g–1); it also shows proton conductivity (1.9 × 10–3 S·cm–1 at 90 °C and 90% relative humidity), which, most notably, increases to a highest value of 3.7 × 10–1 S·cm–1 after oxidizing the −SH into the −SO3H groups.

Direct One-pot Synthesis of Highly Tunable Mixed-linker UiO-66-(SH)2 Metal-Organic Frameworks: Enroute Toward Robust Sulfonic Acid Tagged UiO-66 Architectures

“…XPS investigations were done to examine the influence of PSO on the surface of the mixed-linker thiolated UiO-66 MOFs, as shown in Fig.7ato Fig.7e. The obtained oxidized MOFs contained both aryl thiols/disulfides and sulfonic acids as the PSO was only limited to 1.5 h. This could be confirmed from the presence of relatively lower binding energy (S2p3/2, 163.6-163.7 eV) of thiols/disulfides and relatively higher biding energy (S2p3/2, 168.2-168.5 eV) of sulfonic acid functionalities (ESI; TableS2) 16,39. Hence, the investigation of the S2p spectrum revealed that the PSO was incomplete yet…”

“…S2). 16,39 Hence, the investigation of the S2p spectrum revealed that the PSO was incomplete yet sufficient to trigger structural collapse on activation, especially in U66SO100. FTIR spectroscopy was performed to further validate our findings from surface analysis.…”

Superprotonic conduction of intrinsically zwitterionic microporous polymers based on easy-to-make squaraine, croconaine and rhodizaine dyes

“…Equipping the framework backbones with sulfonic and other acidic groups is a tried-and-true method, as dense arrays of appended -SO 3 H groups can help reach record level of proton conductivity. [12][13][14] Many other functions have been also tried to improve ionic conductivity, including phosphonic acid, 15 Troger's base (for anion exchange membranes), 16 and heterocyclic guests such as 1H-imidazole or 1H-1,2,3-triazole (e.g. for the non-diffusive relay-like proton transport pathway).…”

Remarkable proton conducting behavior driven by synergistic effects in acid–base conjugated MOFs impregnated with sulphuric acid molecules

“…[24][25][26][27] Unlike tightly packed ionic crystals, MOFs have large pore spaces to avoid ion aggregation caused by spatial congestion. [28][29][30][31][32][33][34][35][36][37][38][39][40] Unfortunately, the strategies to further reinforce the proton conductivity by enhancing charge separation are still scarce.…”