Tuning CO2 Uptake and Reversible Iodine Adsorption in Two Isoreticular MOFs through Ligand Functionalization

The synthesis and characterization of two isoreticular metal-organic frameworks (MOFs), {[Cd(bdc)(4-bpmh)]}n⋅2 n(H2O) (1) and {[Cd(2-NH2bdc)(4-bpmh)]}n⋅2 n(H2O) (2) [bdc = benzene dicarboxylic acid; 2-NH2bdc = 2-amino benzene dicarboxylic acid; 4-bpmh = N,N-bis-pyridin-4-ylmethylene-hydrazine], are reported. Both compounds possess similar two-fold interpenetrated 3D frameworks bridged by dicarboxylates and a 4-bpmh linker. The 2D Cd-dicarboxylate layers are extended along the a-axis to form distorted square grids which are further pillared by 4-bpmh linkers to result in a 3D pillared-bilayer interpenetrated framework. Gas adsorption studies demonstrate that the amino-functionalized MOF 2 shows high selectivity for CO2 (8.4 wt % 273 K and 7.0 wt % 298 K) over CH4 , and the uptake amounts are almost double that of non-functional MOF 1. Iodine (I2 ) adsorption studies reveal that amino-functionalized MOF 2 exhibits a faster I2 adsorption rate and controlled delivery of I2 over the non-functionalized homolog 1.