Hydrothermal smectite synthesis in presence of Glycine: Synergistic chemical evolution

The role of smectite surfaces in organic matter dynamics is well documented, with clear evidence of their capacity to concentrate, preserve, and chemically modify organic compounds. However, the reciprocal influence—how organic molecules might guide clay mineral formation—remains a relatively unexplored scientific frontier. The present study investigates the dual role of glycine in Fe-smectite crystallization under hydrothermal conditions (150 °C for 5 days in an inert atmosphere), exploring how this ubiquitous amino acid influences mineral formation processes. X-ray diffraction confirmed the crystallization of Fe-smectite across glycine concentrations ranging from 0.08 to 0.6 M. The increase in glycine concentration induced a decrease in tetrahedral Fe(III) content and promoted the reduction of octahedral Fe(III) to Fe(II), as revealed by X-ray diffraction, Fourier transform infrared spectroscopy, and electrochemical analyses, consequently modifying the measured cation exchange capacity. Glycine polymerization was markedly enhanced in experiments with Fe-smectite crystallization compared to experiments without Fe-smectite. The presence of Fe-smectite favored linear peptides over cyclic one, thus facilitating the production of longer peptide chains. The results reveal a mutual interaction between glycine and minerals, resulting in minerals with distinct structural properties and reactivities that enhance organic matter transformation.