Water stable Cu(II)-based porous Metal-Organic materials for CO2 capture and environmentally application

In the context of the ongoing climate emergency, the study of porous materials takes on a crucial role in addressing environmental challenges. In this respect, the storage and release of different molecules in a controlled manner could be considered one of the most important applications of metal-organic porous materials.[1], [2] In our attempt to obtain new Cu(II)-based porous metal-organic materials, we exploited the use of β-diketone ligands featuring functional groups with N- and O-donor atoms. In particular, reacting the asymmetric β-diketone/carboxylic ligand 1-(4-carboxyphenyl)-3-phenyl-1,3-propanedione) (H21L) [3] with copper acetate we obtained three isostructural Metal-Organic Cages (MOCs) of general formula [Cu16(1L)16(A)n(B)8](S)x [A= THF (tetrahydrofuran), n=8, B=H2O (1); A=diox (dioxane), n=4, B=H2O (2); A = B = dme (dimethoxyethane), n=8 (3). Interestingly, the cages demonstrated remarkable stability in water, and preliminary investigations of their host-guest chemistry indicate that coordinated tetrahydrofuran (THF) molecules in compound 1 can be completely replaced by organic ether molecules. This intriguing behavior is currently being studied for its potential in removing organic pollutants from water. Furthermore, we present findings on the water and CO2 adsorption capabilities of the third-generation water-stable metal-organic framework (MOF) [Cu(2L)(H2O)2]2∙(Xn) (4) (H2L = 1,3-Bis(4-pyridyl)-1,3-propanedione; X=F-, Cl-, Br-, NO3-, BF4-, SO3CF3- , n=2; X=SO42-, n=1). The structure boasts a remarkable 70% of unoccupied space. Notably, it has been observed that the desolvated-amorphous phase of compound 4 can reversibly adsorb significant quantities of water over multiple cycles (at least five). Moreover, CO2 adsorption experiments have unveiled that while minimal gas uptake occurs under dry conditions, the uptake of CO2 experiences a substantial increase when undertaken under humid conditions.