Efficient H2 production from formic acid by a supported iron catalyst on silica

• A novel heterogeneous catalyst FeII/RPPh2@SiO2 for H2-generation from FA.
• Catalytic H2 production at near-ambient temperatures with high activity.
• FeII/RPPh2@SiO2 is stable, reusable, able to generate up to 14 lt of H2 within 6 h.
• The corresponding homogeneous catalyst, FeII/RPPh2, is totally inactive.

Formic acid (FA) represents a convenient H2-source/storage material. Herein, we introduce two highly efficient heterogeneous catalysts for H2-generation from FA, FeII/RPPh2@SiO2 and FeII/polyRPhphos@SiO2, prepared by covalently immobilizing FeII-phosphine-complexes on SiO2 particles. EPR shows that in both the homogeneous and the heterogenized system the Fe atom has similar ligand-field parameters, which indicate a moderately-tight coordination of the Fe atom (D = 0.455 cm−1) that allows rapid substrate accessibility. Heterogenization of the-commonly used –FeII/P(CH2CH2PPh2)3 system, increased its TOF by 170% vs. the homogeneous catalyst. Remarkably, FeII/RPPh2@SiO2 is able to generate up to 14 lt of H2 within 6 h while homogeneous FeII/RPPh2 was totally inactive. Both heterogeneous catalysts are able to produce H2 from FA at near-ambient temperatures (55–90 °C) with no co-catalyst added, with high selectivity and activity, and show excellent stability and reusability.

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