Biogenic transformation of marine diatoms into MFI-type aluminosilicate catalytic interfaces for selective etherification

Abstract

The biosilica of marine diatoms presents a sustainable and architecturally unique platform for the development of catalytic materials through transformation into aluminosilicate. However, previous studies have predominantly employed fossilized diatomite as a silica source instead of renewable diatom cultures. Furthermore, the catalytic activities have primarily been limited to catalytic cracking and pyrolysis, without demonstrating synthesis applications. In this work, we investigated the biogenic transformation of Cyclotella striata TBI marine diatom into MFI-type aluminosilicate, using tetrapropylammonium bromide as an organic structure-directing agent. The resulting materials exhibited porous architectures with an average pore radius of 5.96 nm and a surface area of 60.47 m² g⁻¹. Spectroscopic and microscopic analyses confirmed the formation of polycrystalline MFI-type frameworks with accessible Brønsted acid sites (0.6419 mmol g⁻¹ catalyst). Catalytic etherification of ethanol with tert-butanol exhibited complete selectivity toward ethyl tert-butyl ether (ETBE) without detectable side products, achieving a turnover number of 16.4 mmol ETBE per mol active site. Only the aluminium-incorporated materials were catalytically active for etherification, thus highlighting the role of the engineered aluminosilicate interface in promoting selective reactivity. These findings establish a renewable biomass-to-catalyst pathway for fabricating functional catalytic interfaces in green fuel synthesis.