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)center dot 2n(H2O) (1) and {[Cd(2-NH(2)bdc)(4-bpmh)]}(n)center dot 2n(H2O) (2) [bdc= benzene dicarboxylic acid; 2-NH(2)bdc= 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 I-2 adsorption rate and controlled delivery of I-2 over the non-functionalized homolog 1.