Formamide Adsorption at the Amorphous Silica Surface: A Combined Experimental and Computational Approach

Abstract

Mineral surfaces have been demonstrated to play a central role in prebiotic reactions, which are understood to be at the basis of the origin of life. Among the various molecules proposed as precursors for these reactions, one of the most interesting is formamide. Formamide has been shown to be a pluripotent molecule, generating a wide distribution of relevant prebiotic products. In particular, the outcomes of its reactivity are strongly related to the presence of mineral phases acting as catalysts toward specific reaction pathways. While the mineral–products relationship has been deeply studied for a large pool of materials, the fundamental description of formamide reactivity over mineral surfaces at a microscopic level is missing in the literature. In particular, a key step of formamide chemistry at surfaces is adsorption on available interaction sites. This report aims to investigate the adsorption of formamide over a well-defined amorphous silica, chosen as a model mineral surface. An experimental IR investigation of formamide adsorption was carried out and its outcomes were interpreted on the basis of first principles simulation of the process, adopting a realistic model of amorphous silica.

Monitoring the Reactivity of Formamide on Amorphous SiO2 by In-Situ UV-Raman Spectroscopy and DFT Modeling

“…The four prominent signals observed can be assigned to the symmetric and antisymmetric stretching of the amide moiety (1300 and 1670 cm −1 , respectively), to the in-plane NH2 bending (1600 cm −1 ) and to the in-plane CH bending (1390 cm −1 ). The extended tail toward higher wavenumber characterizing the antisymmetric amide stretching suggests that the formamide molecules are interacting with different species, most probably other formamide molecules or, eventually, silanol groups of the SiO2 surface (in agreement with previous report [30]). In the following hours, several spectral modifications occur, in particular the formation of new bands is observed.…”

Emission of Toxic HCN During NOx Removal by Ammonia SCR in the Exhaust of Lean‐Burn Natural Gas Engines

“…With a minor or no shift, the most intense band at 1691 cm −1 was claimed by several studies as the fingerprint of adsorbed formamide . Further characteristic bands of formamide adsorption were also reported at lower or higher wavenumbers and were assigned to NH, NH 2 , CH or CO groups stretching on α‐Fe 2 O 3 , Fe 2 O 3 /SiO 2 and amorphous silica . These bands could be only partially identified in our study due to the overlap with other adsorbed species, particularly with formates.…”

Role of Mineral Surfaces in Prebiotic Chemical Evolution. In Silico Quantum Mechanical Studies

“…Signorile et al [177] studied the interaction of formamide (FA) on a well-defined amorphous silica model, the results of which were compared with IR measurements. The amorphous silica surface model was derived from a periodic 2D slab [178] with a moderate hydroxylation degree similar to the experimental sample (≈ 1.5 OH nm −2 ) represented by two independent surface silanol (SiOH) groups per unit cell.…”