Grafted metallocalixarenes as single-site surface organometallic catalysts

Justin M. Notestein, Enrique Iglesia, Alexander Katz*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

95 Scopus citations


Metallocalixarenes were grafted onto silica using a surface organometallic approach and shown to be active and selective catalysts for epoxidation of alkenes using organic hydroperoxides. Calixarene-TiIV precursors were anchored at surface densities from 0.1 to near-monolayer coverages (0.025-0.25 calixarene nm-2). Several spectroscopic methods independently detected calixarene-TiIV connectivity before and after epoxidation catalysis. Kinetic analyses of cyclohexene epoxidation confirmed that the active sites were anchored on the silica surface and were significantly more active than their homogeneous analogues. The steric bulk and multidentate binding of the calixarenes led to structural stability and to single-site behavior during epoxidation catalysis. Rate constants were independent of surface density for cyclohexene epoxidation with tert-butyl hydroperoxide (11.1 ± 0.3 M -2 s-1) or cumene hydroperoxide (25 ± 2 M -2 s-1). The materials and methods reported here allow the assembly of robust surface organometallic structures in which the active sites behave as isolated species, even near saturation monolayer coverages. In turn, this makes possible the rational design and synthesis of a class of heterogeneous oxide catalysts with atomic-scale precision at the active site.

Original languageEnglish (US)
Pages (from-to)16478-16486
Number of pages9
JournalJournal of the American Chemical Society
Issue number50
StatePublished - Dec 22 2004

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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