Unlocking High Porosity: Post-Synthetic Solvothermal Treatment of Cu-Paddlewheel Based Metal-Organic Cages.

Metal-organic cages (MOCs) have garnered significant attention due to their unique discrete structures, intrinsic porosity, designability, and tailorability. However, weak inter-cage interactions, such as van der Waals forces and hydrogen bonding can cause solid-state MOCs to lose structural integrity during desolvation, leading to the loss of porosity. In this work, a novel strategy to retain the permanent porosity of Cu-paddlewheel-based MOCs, enabling their use as heterogeneous catalysts is presented. Post-synthetic solvothermal treatments in non-coordinating solvents, mesitylene, and p-xylene, effectively preserve the packing structures of solvent-evacuated MOCs while preventing cage agglomeration. The resulting MOCs exhibit an exceptional N2 sorption capacity, with a high surface area (SBET = 1934 m2 g-1 for MOP-23), which is among the highest reported for porous MOCs. Intriguingly, while the solvothermal treatment reduced Cu(II) to Cu(I) in the Cu-paddlewheel clusters, the MOCs with mixed-valenced Cu(I)/Cu(II) maintained their crystallinity and permanent porosity. The catalytic activities of these MOCs are successfully examined in copper(I)-catalyzed hydrative amide synthesis, highlighting the prospect of MOCs as versatile reaction platforms.

Dual-functional metal-organic framework for chemisorption and colorimetric monitoring of cyanogen chloride.

Given the growing concern over the deployment of toxic chemicals in warfare, the rapid and accurate removal and detection of cyanogen chloride (CK) as a blood agent has become increasingly critical. However, conventional physisorbents and chemisorbents used in military respirators are insufficient for the effective removal of CK. In this study, we demonstrate the chemisorption and sensing abilities of Co2(m-DOBDC) (m-DOBDC4- = 4,6-dioxo-1,3-benzenedicarboxylate) for CK via electrophilic aromatic substitution (EAS) in humid environments. Unlike the chemisorption in triethylenediamine (TEDA) impregnated carbon materials, which generates by-products through hydrolysis, the electron-rich C5 sites in m-DOBDC4- ligands give rise to cyano substitution with CK. This leads to the formation of stable C-C bonds and chloride ions (Cl-) coordinating with open Co2+ sites. Such a mechanism prevents the generation of toxic by-products like cyanic acid and hydrochloric acid. Breakthrough experiments conducted in a packed-bed system conclusively demonstrated the superior CK removal capacity of Co2(m-DOBDC) (1662 min/g), compared to TEDA-impregnated activated carbon (323 min/g) under humid conditions. Considering that MOF-74 series, isostructural with Co2(m-DOBDC), barely adsorb CK under similar conditions, this finding marks a significant advancement in developing novel sorbents for CK removal. Moreover, this chemisorption not only exhibited rapid and highly efficient CK removal but also enabled colorimetric monitoring via the distinctive color change induced by the coordination of Cl- acting as σ donors. These findings facilitate the development of adsorption and sensing equipment to protect military personnel from toxic chemical threats.