Highly-Efficient Reusable [Silica@Iminophosphine-FeII] Hybrids for Hydrogen Production via Formic Acid and Formaldehyde Dehydrogenation.

The use of hybrids, developed by grafting homogeneous catalysts onto supporting materials, has already demonstrated significant potential in various catalytic processes. These systems combine the advantages of homogeneous catalysts, such as high activity and selectivity, with those of solid supports, including enhanced recyclability. Catalytic hydrogen (H2) production via dehydrogenation of C1 organic molecules targeting its use in fuel cells is a contemporary scientific issue directly connected with climate crisis. Here, Iminophospine hybrid [SiO2@benzNP] and its reduced analogue [SiO2@benzNHP] were synthesized, covalently grafted on colloidal SiO2, fully characterized (FT-IR, RAMAN, TGA, ssNMR, BET), and used for in-situ synthesis of [SiO2@benzNP-FeII] and [SiO2@benzNHP-FeII] catalytic complexes for H2 production from formic acid (HCOOH) and formaldehyde (HCHO), at 80 °C. In HCOOH, both heterogenized catalysts exhibit high selectivity, producing H2 and CO2 in a 1 : 1 ratio, without CO contamination, making them ideal for fuel cell applications. [SiO₂@benzNHP-FeII] catalyst demonstrated superior performance in both substates. In HCOOH dehydrogenation, over 82,000 turnover number (TONs) were achieved and retained its efficiency for over five cycles, without any further metal addition. In HCHO dehydrogenation, it showed excellent efficiency as well, achieving 1.3 L of pure H2 with TONs exceeding 7,000, in 3 consecutive uses. Advanced spectroscopic analysis confirmed the stability and structural integrity of the catalysts, linking the Schiff base reduction and N-H groups to enhanced activity, durability and reusability. This study demonstrates the potential of hybrid materials with non-noble metals for cost-effective and sustainable H2 production, paving the way for scalable renewable energy solutions.