Highly Active Silver ion-Exchanged Silicotungstic Acid Catalysts for Selective Esterification of Glycerol with Lauric Acid

Stabilization of {Ag20(StBu)10} and {Ag19(StBu)10} Toroidal Complexes in DMSO: HPLC-ICP-AES, PL, and Structural Studies

The presence of DMSO provides a unique ability to stabilize silver toroidal complexes in the direct reaction between AgStBu and AgNO3 at 80 °C. Slow cooling results in large crystals of [NO3@Ag19.2(StBu)10(DMSO)5.2(NO3)8.2]·3DMSO (1), which were isolated and characterized by single crystal X-ray diffraction (SCXRD) analysis. The crystal structure contains both {Ag20(StBu)10} and {Ag19(StBu)10} clusters. The solution of these material in DMSO was studied with HPLC techniques, which demonstrated the presence of both complexes in solution. The use of [SiW12O40]4– as counter anion gives crystals of a double complex salt [Ag17.8(NO3)3.8(StBu)10][SiW12O40]·30DMSO (2) under the same conditions. Temperature-dependent photoluminescence (PL) was studied.

Versatile Coordination Polymer Catalyst for Acid Reactions Involving Biobased Heterocyclic Chemicals

The chemical valorization/repurposing of biomass-derived chemicals contributes to a biobased economy. Furfural (Fur) is a recognized platform chemical produced from renewable lignocellulosic biomass, and furfuryl alcohol (FA) is its most important application. The aromatic aldehydes Fur and benzaldehyde (Bza) are commonly found in the slate of compounds produced via biomass pyrolysis. On the other hand, glycerol (Gly) is a by-product of the industrial production of biodiesel, derived from fatty acid components of biomass. This work focuses on acid catalyzed routes of Fur, Bza, Gly and FA, using a versatile crystalline lamellar coordination polymer catalyst, namely [Gd(H4nmp)(H2O)2]Cl·2H2O (1) [H6nmp=nitrilotris(methylenephosphonic acid)] synthesized via an ecofriendly, relatively fast, mild microwave-assisted approach (in water, 70 °C/40 min). This is the first among crystalline coordination polymers or metal-organic framework type materials studied for the Fur/Gly and Bza/Gly reactions, giving heterobicyclic products of the type dioxolane and dioxane, and was also effective for the FA/ethanol reaction. 1 was stable and promoted the target catalytic reactions, selectively leading to heterobicyclic dioxane and dioxolane type products in the Fur/Gly and Bza/Gly reactions (up to 91% and 95% total yields respectively, at 90 °C/4 h), and, on the other hand, 2-(ethoxymethyl)furan and ethyl levulinate from heterocyclic FA.