Grafted metallocalixarenes as single-site surface organometallic catalysts

Justin M. Notestein, Enrique Iglesia, Alexander Katz

Research output: Contribution to journalArticle

84 Citations (Scopus)

Abstract

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
Pages (from-to)16478-16486
Number of pages9
JournalJournal of the American Chemical Society
Volume126
Issue number50
DOIs
Publication statusPublished - Dec 22 2004

ASJC Scopus subject areas

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

Fingerprint Dive into the research topics of 'Grafted metallocalixarenes as single-site surface organometallic catalysts'. Together they form a unique fingerprint.

  • Cite this