Surface cavities formed by molecularly rigid polymers of intrinsic microporosity affect catalytic processes. Palladium nanoparticles of typically 3 nm diameter are formed in an intrinsically microporous polyamine (PIM-EA-TB) by borohydride reduction. These particles are shown to indirectly catalyse the oxidative colour change of indicator dye 3,5,3′,5′-tetramethylbenzidine (TMB) in the presence of formic acid via formation of H2O2. Investigation reveals that oxygen reduction on the palladium is rate limiting with optimised H2O2 production at approximately pH 3 to 4, and first order in formate, followed by purely homogeneous TMB oxidation. The H2O2 production is therefore studied separately as a nanozyme-like catalytic process equivalent to formate oxidase reactivity, linked to the molecularly rigid polyamine host (PIM-EA-TB) providing ammonium sites (in molecularly rigid surface cavities) that enhance both (i) 2-electron formate oxidation and (ii) 2-electron oxygen reduction to H2O2. Beneficial effects of hydrophobic ClO4- anions are noted as indirect evidence for the effect of ammonium sites in surface cavities. A computational DFT model for the artificial formate oxidase reactivity is developed to underpin and illustrate the hypothesis of PIM-EA-TB as an active catalyst component with implications for future nanozyme sensor development.

Original languageEnglish
Pages (from-to)253-266
Number of pages14
JournalJournal of Catalysis
Early online date17 Nov 2022
Publication statusPublished - 31 Dec 2022

Bibliographical note

L.W. thanks the China Scholarship Council (201906870022) for a PhD stipend. F.M. thanks EPSRC for support under project EP/K004956/1. We also acknowledge Supercomputing Wales for access to the Hawk HPC facility, part-funded by the European Regional Development Fund via the Welsh Government.


  • Bipolar catalyst
  • Cavity catalysis
  • Clark probe
  • Disinfection
  • Nanozyme
  • Oxidase

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry


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