Direct air capture (DAC) shows considerable promise for the effective removal of CO₂; however, materials applicable to DAC are lacking. Among metal-organic framework (MOF) adsorbents, diamine-Mg₂(dobpdc) (dobpdc^4- = 4,4-dioxidobiphenyl-3,3'-dicarboxylate) effectively removes low-pressure CO₂, but the synthesis of the organic ligand requires high temperature, high pressure, and a toxic solvent. Besides, it is necessary to isolate the ligand for utilization in the synthesis of the framework. In this study, we synthesized a new variant of extended MOF-74-type frameworks, M₂(hob) (M = Mg²⁺, Co²⁺, Ni²⁺, and Zn²⁺; hob^4- = 5,5'-(hydrazine-1,2-diylidenebis(methanylylidene))bis(2-oxidobenzoate)), constructed from an azine-bonded organic ligand obtained through a facile condensation reaction at room temperature. Functionalization of Mg₂(hob) with <i>N</i>-methylethylenediamine, <i>N</i>-ethylethylenediamine, and <i>N</i>,<i>N</i>'-dimethylethylenediamine (mmen) enables strong interactions with low-pressure CO₂, resulting in top-tier adsorption capacities of 2.60, 2.49, and 2.91 mmol g^-1 at 400 ppm of CO₂, respectively. Under humid conditions, the CO₂ capacity was higher than under dry conditions due to the presence of water molecules that aid in the formation of bicarbonate species. A composite material combining mmen-Mg₂(hob) and polyvinylidene fluoride, a hydrophobic polymer, retained its excellent adsorption performance even after 7 days of exposure to 40% relative humidity. In addition, the one-pot synthesis of Mg₂(hob) from a mixture of the corresponding monomers is achieved without separate ligand synthesis steps; thus, this framework is suitable for facile large-scale production. This work underscores that the newly synthesized Mg₂(hob) and its composites demonstrate significant potential for DAC applications.

Direct air capture (DAC) shows considerable promise for the effective removal of CO₂; however, materials applicable to DAC are lacking. Among metal-organic framework (MOF) adsorbents, diamine-Mg₂(dobpdc) (dobpdc^4- = 4,4-dioxidobiphenyl-3,3'-dicarboxylate) effectively removes low-pressure CO₂, but the synthesis of the organic ligand requires high temperature, high pressure, and a toxic solvent. Besides, it is necessary to isolate the ligand for utilization in the synthesis of the framework. In this study, we synthesized a new variant of extended MOF-74-type frameworks, M₂(hob) (M = Mg²⁺, Co²⁺, Ni²⁺, and Zn²⁺; hob^4- = 5,5'-(hydrazine-1,2-diylidenebis(methanylylidene))bis(2-oxidobenzoate)), constructed from an azine-bonded organic ligand obtained through a facile condensation reaction at room temperature. Functionalization of Mg₂(hob) with <i>N</i>-methylethylenediamine, <i>N</i>-ethylethylenediamine, and <i>N</i>,<i>N</i>'-dimethylethylenediamine (mmen) enables strong interactions with low-pressure CO₂, resulting in top-tier adsorption capacities of 2.60, 2.49, and 2.91 mmol g^-1 at 400 ppm of CO₂, respectively. Under humid conditions, the CO₂ capacity was higher than under dry conditions due to the presence of water molecules that aid in the formation of bicarbonate species. A composite material combining mmen-Mg₂(hob) and polyvinylidene fluoride, a hydrophobic polymer, retained its excellent adsorption performance even after 7 days of exposure to 40% relative humidity. In addition, the one-pot synthesis of Mg₂(hob) from a mixture of the corresponding monomers is achieved without separate ligand synthesis steps; thus, this framework is suitable for facile large-scale production. This work underscores that the newly synthesized Mg₂(hob) and its composites demonstrate significant potential for DAC applications.

Acoustic energy transfer using ferroelectrically augmented triboelectric receivers can efficiently deliver energy to implantable medical devices, marine cable operation sensors, and electronic devices with electromagnetic interference shielding cases.

While strategies for proton conductivity enhancement are required, appropriate synthetic procedures are still sought. Herein, we synthesized a porous organic polymer, POP-Me40, through the judicial selection of functional groups with varying electronic effects. Postsynthetic sulfonation of POP-Me40 was conducted to produce POP-Me40-S. This material demonstrates a high conductivity of 1.42 × 10^-1 S cm^-1 at 80 °C and 90% relative humidity along with a low activation energy of 0.094 eV, consistent with the Grotthuss proton conduction mechanism. Subsequent impregnation of sulfonic acid groups in POP-Me40-S afforded a doubly acidified polymer, POP-Me40-S-SA, showing an exceptional proton conductivity of 1.91 × 10^-1 S cm^-1 under the same conditions. This value represents a 780000-fold increase in conductivity with respect to its unmodified precursor, POP-Me40, setting a record among porous materials. Furthermore, POP-Me40-S-SA exhibits an activation energy of 0.063 eV, one of the lowest reported, indicating the formation of highly efficient proton transport pathways within its framework channels.