Barocaloric Effects in Dialkylammonium Halide Salts.

Barocaloric effects─solid-state thermal changes induced by the application and removal of hydrostatic pressure─offer the potential for energy-efficient heating and cooling without relying on volatile refrigerants. Here, we report that dialkylammonium halides─organic salts featuring bilayers of alkyl chains templated through hydrogen bonds to halide anions─display large, reversible, and tunable barocaloric effects near ambient temperature. The conformational flexibility and soft nature of the weakly confined hydrocarbons give rise to order-disorder phase transitions in the solid state that are associated with substantial entropy changes (>200 J kg K) and high sensitivity to pressure (>24 K kbar), the combination of which drives strong barocaloric effects at relatively low pressures.

A Structure-Activity Study of Aromatic Acid Modulators for the Synthesis of Zirconium-Based Metal-Organic Frameworks.

Acid modulation is among the most widely employed methods for preparing metal-organic frameworks (MOFs) that are both stable and highly crystalline, yet there exist few guiding principles for selecting the optimal modulator for a given system. Using the Zr-based MOFs UiO-66 and UiO-68-Me (UiO = Universitetet i Oslo) as representative materials, here we present for the first time an in-depth structure-activity study of acid modulators and identify key principles of modulation for the synthesis of highly crystalline Zr-MOFs. By applying whole pattern fitting of powder X-ray diffraction (PXRD) patterns as a technique for evaluating modulator efficacy, complemented by scanning electron microscopy (SEM), H NMR, and thermogravimetric analysis (TGA), we demonstrate that the key to effective modulation is competition between the linker and modulator for coordination to the Zr secondary building units (SBUs).

Biocompatible metal-organic frameworks for the storage and therapeutic delivery of hydrogen sulfide.

Hydrogen sulfide (HS) is an endogenous gasotransmitter with potential therapeutic value for treating a range of disorders, such as ischemia-reperfusion injury resulting from a myocardial infarction or stroke. However, the medicinal delivery of HS is hindered by its corrosive and toxic nature. In addition, small molecule HS donors often generate other reactive and sulfur-containing species upon HS release, leading to unwanted side effects.