Immobilization of Poly(diamine)phosphazene in an Amine-Functionalized Metal Organic Framework to Enhance Base Catalysis and CO₂ Adsorption

The immobilization of poly(diamine)phosphazene (PP) onto the NH2-MIL-125 metal organic framework (MOF) by a wet impregnation method enhanced the basicity of the MOF. Interestingly, the immobilization also increased the surface area of the MOF due to the opening of inaccessible micropores. The highest immobilization (∼86%) was achieved using a 1 wt % PP solution in acetonitrile, and the resulting material exhibited the best performance in base catalysis. The immobilization using higher concentrations of PP reduced the catalytic activity due to the formation of PP agglomerates or coiled molecules in the framework and the increased microporosity of the material, slowing down the reactants’ diffusion. However, materials with higher loadings of PP showed improved CO2 adsorption due to the increased basicity and microporosity (surface area). The study revealed the specific interactions between polymer and MOF, underscoring the structural integration at the molecular level. The established protocol could be applied to modify amine-functionalized porous materials to improve base catalysis and CO2 adsorption.