Influence of gas packing and orientation on FTIR activity for CO chemisorption to the Cu paddlewheel

Cheng Yu Wang, Paramita Ray, Qihan Gong, Yonggang Zhao, Jing Li, Angela D. Lueking

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23 Scopus citations


In situ Fourier-transform infrared (FTIR) spectroscopy is able to probe structural defects via site-specific adsorption of CO to the Cu-BTC (BTC = 1,3,5-benzenetricarboxylate) metal-organic framework (MOF). The temperature-programmed desorption (TPD) of CO chemisorbed to Cu-TDPAT (TDPAT = 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine) is virtually identical to Cu-BTC, suggesting CO chemisorbs to the open metal site at the axial position of the copper paddlewheel that is the building unit of both MOFs. Yet, despite an increased gravimetric CO : Cu ratio, CO chemisorbed to Cu-TDPAT is FTIR inactive. We rule out the presence of residual solvent, thermal degradation, adsorption temperature, and ligand-induced electronic effects at the adsorption site. TPD at increased pressure suggests the multiple CO per Cu site rearrange in Cu-TDPAT as a dynamic function of temperature and pressure. Thus, the FTIR inactivity of CO chemisorbed to Cu-TDPAT is attributed to orientation and/or packing of the CO relative to the Cu binding site. The results suggest dynamic chemisorption complicate extension of a site-specific in situ FTIR probe of gas adsorption. For both Cu-BTC and Cu-TDPAT, the in situ FTIR probe is a less sensitive probe of defects than X-ray photoelectron spectroscopy and nitrogen adsorption.

Original languageEnglish (US)
Pages (from-to)26766-26776
Number of pages11
JournalPhysical Chemistry Chemical Physics
Issue number40
StatePublished - Sep 7 2015

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry


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