Empowering CO2 Eco-Refrigeration With Colossal Breathing-Caloric-Like Effects in MOF-508b.

Today, ≈20% of the electric consumption is devoted to refrigeration; while, ≈50% of the final energy is dedicated to heating applications. In this scenario, many cooling devices and heat-pumps are transitioning toward the use of CO2 as an eco-friendly refrigerant, favoring carbon circular economy. Nevertheless, CO2 still has some limitations, such as large operating pressures (70-150 bar) and a critical point at 31 °C, which compromises efficiency and increases technological complexity. Very recently, an innovative breathing-caloric mechanism in the MIL-53(Al) compound is reported, which implies gas adsorption under CO2 pressurization boosted by structural transitions and which overcomes the limitations of stand-alone CO2. Here, the breathing-caloric-like effects of MOF-508b are reported, surpassing by 40% those of MIL-53(Al). Moreover, the first thermometry device operating at room temperature and under the application of only 26 bar of CO2 is presented. Under those conditions, this material presents values of ΔT ≈ 30 K, reaching heating temperatures of 56 °C and cooling temperatures of -10 °C, which are already useful for space heating, air-conditioning, food refrigeration, and freezing applications.

Nucleosteroids: carbocyclic nucleoside analogs of androst-4-en-17 beta-ol.

Steroidal nucleoside analogs were synthesized starting from testosterone. By reduction of the oxime of 17 beta-hydroxy-androst-4-en-3-one (testosterone), a mixture of the two amino epimers of C-3 were obtained. The 3 alpha-amino-androst-4-en-17 beta-ol was crystallized in 73% yield and coupled with 5-amino-4,6-dichloropyrimidine to give 3 alpha-(5'-amino-4'-chloro-pyrimidin-6'-yl)amino-androst-4-en-17 beta-ol. This compound was treated with triethyl orthoformate in acid media to give the corresponding purinyl steroid adduct 3 alpha-(6'-chloro-purin-9'-yl)-androst-4-en-17 beta-ol in 98% yield. This substance, in turn, was converted with good yield into the 6'-thio, 6'-methylamino, and 6'-diethyl aminopurinyl derivatives through nucleophilic reactions at C-6 of the purine nucleus.