An attractive method for valorization of glycerol is the catalytic transformation to lactic acid. By overcoming the solubility challenge associated with known homogeneous catalysts for this reaction, we show that thermally robust Ir(I), Ir(III), and Ru(II) N-heterocyclic carbene (NHC) complexes with sulfonate-functionalized wingtips are highly prolific for this process, requiring no cosolvents other than aqueous base. The activity of the catalysts is compared under both conventional heating and microwave conditions. The most active catalyst reaches a TOF of 45 592 h −1 (microwave) and 3477 h −1 (conventional) with 1 equiv of KOH, and proceeds at a constant rate for at least 8 h. Although higher activity is observed with KOH, the catalysts are also highly active with the weaker base, K 2 CO 3 (13 000 h −1 and concurrent formation of formate). The protocol can be modified to achieve quantitative conversion of glycerol in only 3 h. The high activity of these catalysts compared to nonsulfonated analogs is attributed to the stabilization the lactate product in aqueous media. The most active catalyst retains equal activity for crude glycerol. A mechanism is proposed for the most active catalyst precursor involving O−H oxidative addition of glycerol.

Two series of lanthanide metal–organic frameworks (MOFs) formulated as {Ln2(TBrTA)3­(H2O)8­·2H2O} n [Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Dy (9)] series 1, {[Ln3(TBrTA)6]­[Ln­(H2O)8]­·6H2O} n [Ln = Ho (10), Er (11), Tm (12), Yb (13), Lu (14)] series 2, respectively, were synthesized via slow evaporation with tetrabromoterephthalic acid (H2TBrTA) and structurally characterized by X-ray crystallography, infrared spectroscopy, and thermal analysis. Lanthanide contraction effects result in a change in the structure from a two-dimensional (2D) MOF with sql topology for La–Dy (series 1) to a three-dimensional (3D) MOF with pcu network topology for Ho–Lu (series 2). Supramolecular interactions also evolve from Br···Br, Br···O, π–π, and hydrogen bonding interactions in series 1 to Br···Br and hydrogen bonding interactions in series 2. The nature of Br···Br interactions transition from a combination of type I, type II, and quasi-type I/type II in series 1 to only type II in series 2. Furthermore, as the size of the Ln­(III) ion decreases, the strength of the type II Br···Br interactions increases. The anionic frameworks in series 2 are charge balanced by [Ln­(H2O)8]3+ cations in the pores that are encapsulated by an unprecedented three-dimensional (3D) “Star of David” dodecamer water cluster. Photophysical studies demonstrate that TBrTA is an efficient sensitizer of Eu3+(5D0) and Tb3+(5D4) luminescence as excitation into ligand bands leads to bright red and green emission, respectively, the spectral profiles of which display only metal centered emission bands. Emission from compound 6 is significantly quenched in the presence of Fe3+ (87%) and Cu2+ (75%) ions mainly due to competitive absorption of excitation energy, which leads to an inner-filter effect. In addition, the emission of 6 is more than 85% quenched by nitroaromatic compounds (NACs) such as 4-nitrophenol, dinitrophenol, and trinitrophenol (picric acid) with competitive absorption, photoinduced electron transfer, and electrostatic processes the main mechanisms of quenching. This study is the first to show that X···X interactions in extended structures such as MOFs can be tuned with the lanthanide contraction and also reveals that Ln-TBrTA MOFs can be used as bifunctional sensors for the detection of Fe3+ and Cu2+ as well as explosive nitroaromatics.

A new thorium metal‐organic framework (MOF), Th(OBA)2, where OBA is 4,4′‐oxybis(benzoic) acid, has been synthesized hydrothermally in the presence of a range of nitrogen‐donor coordination modulators. This Th‐MOF, described herein as GWMOF‐13, has been characterized by single‐crystal and powder X‐ray diffraction, as well as through a range of techniques including gas sorption, thermogravimetric analysis (TGA), solid‐state UV/Vis and luminescence spectroscopy. Single‐crystal X‐ray diffraction analysis of GWMOF‐13 reveals an interesting, high symmetry (cubic Iatrue3‾ d) structure, which yields a novel srs‐a topology. Most notably, TGA analysis of GWMOF‐13 reveals framework stability to 525 °C, matching the thermal stability benchmarks of the UiO‐66 series MOFs and zeolitic imidazolate frameworks (ZIFs), and setting a new standard for thermal stability in f‐block based MOFs.

Six new uranyl hybrid materials have been synthesized solvothermally utilizing the ligands 2,2′-bipyridine-3,3′-dicarboxylic acid (H 2 L) and 2,2′:6′,2′′-terpyridine (TPY). The six compounds are classified as either molecular complexes ( 6). A discussion of the influence of transition metal incorporation, chelating effects of the ligand, and synthesis conditions on the formation of uranyl materials is presented. The structure of compound 6 is of particular note due to large channel-like voids with a diameter of approximately 19.6 Å.

Bending the linear uranyl (UO) cation represents both a significant challenge and opportunity within the field of actinide hybrid materials. As part of related efforts to engage the nominally terminal oxo atoms of uranyl cation in noncovalent interactions, we synthesized a new uranyl complex, [UO(CHN)(CHClO)]·2HO (complex 2), that featured both deviations from equatorial planarity and uranyl linearity from simple hydrothermal conditions. Based on this complex, we developed an approach to probe the nature and origin of uranyl bending within a family of hybrid materials, which was done via the synthesis of complexes 1-3 that display significant deviations from equatorial planarity and uranyl linearity (O-U-O bond angles between 162° and 164°) featuring 2,4,6-trihalobenzoic acid ligands (where Hal = F, Cl, and Br) and 1,10-phenanthroline, along with nine additional "nonbent" hybrid materials that either coformed with the "bent" complexes (4-6) or were prepared as part of complementary efforts to understand the mechanism(s) of uranyl bending (7-12). Complexes were characterized via single crystal X-ray diffraction and Raman, infrared (IR), and luminescence spectroscopy, as well as via quantum chemical calculations and density-based quantum theory of atoms in molecules (QTAIM) analysis. Looking comprehensively, these results are compared with the small library of bent uranyl complexes in the literature, and herein we computationally demonstrate the origin of uranyl bending and delineate the energetics behind this process.