Changing the Mechanism for CO2 Hydrogenation Using Solvent‐Dependent Thermodynamics

A critical scientific challenge for utilization of CO₂ is the development of catalyst systems that function in water and use inexpensive and environmentally friendly reagents. We have used thermodynamic insights to predict and demonstrate that the HCo^I(dmpe)₂ catalyst system, previously described for use in organic solvents, can hydrogenate CO₂ to formate in water with bicarbonate as the only added reagent. Replacing tetrahydrofuran as the solvent with water changes the mechanism for catalysis by altering the thermodynamics for hydride transfer to CO₂ from a key dihydride intermediate. The need for a strong organic base was eliminated by performing catalysis in water owing to the change in mechanism. These studies demonstrate that the solvent plays a pivotal role in determining the reaction thermodynamics and thereby catalytic mechanism and activity.     

Solvent‐Induced Control over Breathing Behavior in Flexible Metal–Organic Frameworks for Natural‐Gas Delivery

Finding appropriate stimuli for controlling the breathing behavior of flexible metal–organic frameworks (MOFs) is highly challenging. Herein, we report the solvent‐induced changes in the particle size and stability of different breathing phases of the MIL‐53 series, a group of flexible MOFs. A water/dimethylformamide (DMF) ratio is tuned to synthesize members of the MIL‐53 series which have different behaviors. The breathing is explored by high‐pressure methane sorption tests. Increasing DMF concentration decreases MOF particle size and increases the stability of the porous phases, boosting the 5.8–65 bar sorption difference of methane, which is required for natural‐gas delivery.     

Über den Drehwert Einblicke in die Solvathülle gewinnen

The optical rotation of a chiral molecule is more than just a constant. Just like any other physical property, it depends on the exact environmental conditions under which it is measured. Introducing the example of propylene oxide, we show how this supposedly simple molecular property is significantly affected by the behavior and arrangement of the surrounding solvent environment.     

Compensation of London Dispersion in the Gas Phase and in Aprotic Solvents

The importance of London dispersion for structure and stability of molecules with less than about 200 atoms has been established in recent years but the quantitative understanding is still largely based on computations because of a persistent lack of suitable experimental data. We herein report a comprehensive computational and experimental study of the compensation of London dispersion in proton‐bound dimer dissociations showing that total compensation is largely invariant in both polar and nonpolar aprotic solvents spanning a wide range of bulk polarizabilities. Additionally, we find that compensation by solvent (which is about 40–80 %) largely dominates over compensation in the gas phase (which is about 0–40 %) for typical experimental temperatures.     

Temperature‐Driven Planar Chirality Switching of a Pillar[5]arene‐Based Molecular Universal Joint

The study of an enantiopure bicyclic pillar[5]arene‐based molecular universal joint (MUJ) by single‐crystal X‐ray diffraction allowed for the first time the unequivocal assignment of the absolute configuration of a planar chiral pillar[5]arene by circular dichroism spectroscopy. Crucially, the absolute configuration of the MUJ was switched reversibly by temperature, with an accompanying sign inversion of the anisotropy factor that varied by as much as 0.03, which is the largest value ever reported. Mechanistically, the reversible chirality switching of the MUJ is driven by the threading/dethreading motion of the fused ring and hence is dependent on both the size and nature of the ring and the solvent employed, reflecting the critical balance between the self‐complexation of the ring by pillar[5]arene, the solvation to the excluded ring, and the inclusion of solvent molecules in the cavity.     

A Ternary Solvent Method for Large‐Sized Two‐Dimensional Perovskites

Recent reports demonstrate that a two‐dimensional (2D) structural characteristic can endow perovskites with both remarkable photoelectric conversion efficiency and high stability, but the synthesis of ultrathin 2D perovskites with large sizes by facile solution methods is still a challenge. Reported herein is the controlled growth of 2D (C₄H₉NH₃)₂PbBr₄ perovskites by a chlorobenzene‐dimethylformide‐acetonitrile ternary solvent method. The critical factors, including solvent volume ratio, crystallization temperature, and solvent polarity on the growth dynamics were systematically studied. Under optimum reaction condition, 2D (C₄H₉NH₃)₂PbBr₄ perovskites, with the largest lateral dimension of up to 40 μm and smallest thickness down to a few nanometers, were fabricated. Furthermore, various iodine doped 2D (C₄H₉NH₃)₂PbBr_x I_4−x perovskites were accessed to tune the optical properties rationally.     

Graphene Oxide Facilitates Solvent‐Free Synthesis of Well‐Dispersed,Faceted Zeolite Crystals

Zeolites with molecular dimension pores are widely used in petrochemical and fine‐chemical industries. While traditional solvothermal syntheses suffer from environmental, safety, and efficiency issues, the newly developed solvent‐free synthesis is limited by zeolite crystal aggregation. Herein, we report well‐dispersed and faceted silicalite ZSM‐5 zeolite crystals obtained using a solvent‐free synthesis facilitated by graphene oxide (GO). The selective interactions between the GO sheets and different facets, which are confirmed by molecular dynamics simulations, result in oriented growth of the ZSM‐5 crystals along the c‐axis. More importantly, the incorporation of GO sheets into the ZSM‐5 crystals leads to the formation of mesopores. Consequently, the faceted ZSM‐5 crystals exhibit hierarchical pore structures. This synthetic method is superior to conventional approaches because of the features of the ZSM‐5 zeolite.     

Fast and Minimal‐Solvent Production of Superinsulating Silica Aerogel Granulate

With their low thermal conductivity (λ ), silica aerogels can reduce carbon emissions from heating and cooling demands, but their widespread adoption is limited by the high production cost. A one‐pot synthesis for silica aerogel granulate is presented that drastically reduces solvent use, production time, and global warming potential. The inclusion of the hydrophobization agent prior to gelation with a post‐gelation activation step, enables a complete production cycle of less than four hours at the lab scale for a solvent use close to the theoretical minimum, and limits the global warming potential. Importantly, the one‐pot aerogel granulate retains the exceptional properties associated with silica aerogel, mostly λ =14.4±1.0 mW m⁻¹⋅K⁻¹ for the pilot scale materials, about half that of standing air (26 mW m⁻¹⋅K⁻¹). The resource‐, time‐, and cost‐effective production will allow silica aerogels to break out of its niche into the mainstream building and industrial insulation markets.     

Voltage‐Switchable HCl Transport Enabled by Lipid Headgroup–Transporter Interactions

Synthetic anion transporters that facilitate transmembrane H⁺/Cl^? symport (cotransport) have anti‐cancer potential due to their ability to neutralize pH gradients and inhibit autophagy in cells. However, compared to the natural product prodigiosin, synthetic anion transporters have low‐to‐modest H⁺/Cl^? symport activity and their mechanism of action remains less well understood. We report a chloride‐selective tetraurea macrocycle that has a record‐high H⁺/Cl^? symport activity similar to that of prodigiosin and most importantly demonstrates unprecedented voltage‐switchable transport properties that are linked to the lack of uniport activity. By studying the anion binding affinity and transport mechanisms of four other anion transporters, we show that the lack of uniport and voltage‐dependent H⁺/Cl^? symport originate from strong binding to phospholipid headgroups that hampers the diffusion of the free transporters through the membrane, leading to an unusual H⁺/Cl^? symport mechanism that involves only charged species. Our work provides important mechanistic insights into different classes of anion transporters and a new approach to achieve voltage‐switchability in artificial membrane transport systems.