Adsorption of nitric oxide in metal-organic frameworks: Low temperature IR and EPR spectroscopic evaluation of the role of open metal sites

The metal-organic framework materials M-MIL-100 (M = Al, Fe) and M-CPO-27 (M = Co, Ni) have been studied with respect to the adsorption of nitric oxide employing low-temperature ESR and IR spectroscopy. Exposure of the previously desolvated Ni (II) and Co (II) sites in CPO-27 leads to the formation of metal nitrosyl complexes that are stable up to temperatures of 393 K. A weaker bond is formed between the iron metal centers in the Fe-MIL-100 type materials and the nitric oxide molecule. Using in-situ DRIFT and EPR spectroscopy at low temperatures, the formation of Co-, Ni- and Fe-NO adducts is evident from the respective spectra, while specifically strong interactions are absent in Al-MIL-100 and Al/Cr-Mil-53. (C) 2015 Published by Elsevier Inc.