Strong CO2 Chemisorption in a Metal-Organic Framework with Proximate Zn-OH Groups

A novel Zn benzotriazolate metal-organic frame-work (MOF), [Zn9(OAc)6(bbtm)6] (1, bbtm2- = bis-(benzotriazolyl)methanone, OAc- = acetate), has been synthesized and structurally characterized using micro-crystal electron diffraction. The framework contains 12-connected nonanuclear Zn clusters with Zn-OAc groups separated by short intercluster ZnmiddotmiddotmiddotZn distances of 6.06 A. Postsynthetic OAc-/OH- ligand exchange followed by thermal activation generates 1a-OH, which adsorbs CO2 at very low pressures (1.37 mmol/g at 2.5 mbar) and requires an unusually high desorption temperature (>160 degrees C). Diffuse reflectance IR Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations have been used to interrogate the CO2 binding mechanism in 1a-OH. The formation of unsymmetric bridging carbonate ligands within the ZnmiddotmiddotmiddotZn pockets accompanied by strong hydrogen bonding of the carbonate with a neighboring zinc aqua ligand explains the remarkably strong CO2 affinity of 1a-OH.

Automated summary

A novel Zn benzotriazolate metal-organic framework with strong CO2 adsorption capacity has been synthesized and characterized. The framework exhibits high desorption temperature.