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Receptor-Based Adsorbent Crystals Assembled with B←N Adducts for Molecular Recognition of Refractory Aromatic Sulfur Compounds in Model Fuels
Journal article

Receptor-Based Adsorbent Crystals Assembled with B←N Adducts for Molecular Recognition of Refractory Aromatic Sulfur Compounds in Model Fuels

Alain D. Celis-Villegas, Angel D. Herrera-España, Christian Rodríguez-Ruiz, Marina A. Ortega-Rojas, Celymar Ortiz de Leon, Karina Mondragón-Vásquez, Marcos Flores-Alamo, Cercis Morera-Boado, Leonard R. MacGillivray, Herbert Höpfl, …
Crystal Growth & Design
06/10/2026
DOI: 10.1021/acs.cgd.6c00043

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Abstract

The presence of refractory aromatic sulfur compounds in fossil fuels needs to be eliminated or reduced to minimize the emissions of sulfur oxides that cause serious environmental and health problems. In this work, we investigated the ability of three crystalline adducts A1, A2, and A3, constituted of phenyl, 1-naphthyl, or 2-naphthyl boronic esters linked to 3,6-di(pyridin-4-yl)-1,2,4,5-tetrazine (BiPyTz) through dative B←N bonds, to generate cocrystals with refractory aromatic sulfur compounds such as dibenzothiophene (DBT), 4-methyldibenzothiophene (4MDBT), and 4,6-dimethyldibenzothiophene (46DMDBT). Only compound A2 crystallized into the corresponding (1:1) cocrystal with 4MDBT and 46DMDBT (i.e., A2·4MDBT and A2·46DMDBT). Furthermore, crystalline A2 effectively removed 46DMDBT in batch sorption experiments with a single-component solution in isooctane, where quantitative conversion of A2 to A2·46DMDBT occurs within 2 h at 25 °C. In a three-component model fuel solution, uptake was particularly successful for the bulkier derivative 46DMDBT, and the efficiency followed the trend 46DMDBT > 4MDBT ≫ DBT. The X-ray crystal structure of A2·46DMDBT exhibits a binding pocket assembled with four neighboring adducts, anchoring the guest molecule by using multiple noncovalent interactions with BiPyTz (Cπ···Cπ, S···N, N···Cπ), and with the aromatic moieties of the boronic ester (C–H···Cπ and C–H···O). Computational analysis of model A2–guest complexes showed bond critical points (AIM) for these reciprocal donor–acceptor aromatic interactions, and computation of the energies confirmed the greater stability of the complex A2–46DMDBT. Thus, the superior molecular recognition ability of the receptor-based crystal A2 is sustained using electron-deficient BiPyTz to incite significant donor–acceptor interactions with the electron-rich guest, accompanied by the adaptive behavior of the B←N receptor leading to subtle conformational changes to engage the 1-naphthyl moiety in the assembly of the binding pocket to effectively remove methylated refractory sulfur compounds from fuels under friendly conditions.
Crystallography Cell Parameters Crystal Structure Crystal System Experimental 3D Coordinates Space Group

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