The metal organic framework (MOF) UHM-3, constructed with Cu(II)-paddle wheel-type nodes and a new tetracarboxylic acid linker, 5,5′-(dimethylsilanediyl)diisophthalate, has a close-packed alignment of open Cu(II) sites which are of interest for applications in gas storage and separation. Here, we first report on the growth of oriented, homogeneous and virtually defect-free (below 1%) UHM-3 MOF thin films on a solid substrate using a room-temperature liquid phase epitaxy (LPE) method. Thermal postsynthetic treatment allowed to induce Cu(I) defect sites in a controlled fashion. The interaction of CO and CO2 with the Cu(II) and Cu(I) sites was then studied using X-ray photoelectron spectroscopy (XPS) and IR-spectroscopy. The binding energy of these two species was determined using temperature-induced desorption. The interaction between the guest molecules and the Cu(I) and Cu(II) sites were also analyzed using density-functional theory (DFT). Surprisingly, both experiment and theory show that the binding energy of CO2 to Cu(I) and Cu(II) sites are essentially identical, in pronounced contrast to CO, which binds much stronger to Cu(I).
Bibliographical noteFunding Information:
Financial support by Deutsche Forschungsgemeinschaft (DFG) within the Priority Program Metal−Organic Frameworks (SPP 1362) is gratefully acknowledged. Z. Wang and C. Yang thank the Chinese Scholarship Council (CSC No. 2011695014) for their financial support. Advice and experimental help from Dr. S. Grosjean and Prof. S. Braese (Institute for Organic Chemistry, KIT) is greatly appreciated.
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All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials