Epoxidation of vegetable oil's double bonds by nickel single-atoms stabilized in graphitic carbon nitrides: sustainable monomers for epoxy thermoset polymer composites

• Grant number: 21/14792-2
• Support Opportunities: Regular Research Grants
• Start date: May 01, 2022
• End date: April 30, 2023
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Inorganic Chemistry
• Agreement: Delft University of Technology
• Mobility Program: SPRINT - Projetos de pesquisa - Mobilidade
• Principal Investigator: Ivo Freitas Teixeira
• Grantee: Ivo Freitas Teixeira
• Principal researcher abroad: Baris Kumru
• Institution abroad: Delft University of Technology (TU Delft), Netherlands
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 20/14741-6 - Graphitic carbon nitrides as platforms for single-atom photocatalysis: moving towards design principles for improved performance, AP.JP

Abstract

This proposal aims to produce epoxide monomers from vegetable oil photoepoxidation. The heterogeneous photocatalysts which will be employed for this task will be nickel single-atoms stabilized in poly(heptazine imides) (PHI). Poly(heptazine imides) are polymeric semiconductor composed of only atoms of carbon and nitrogen (carbon nitride-based material) which its framework is composed of heptazine units. Recently, poly(heptazine imides) were applied to host single atoms of different metals. These highly crystalline type of carbon nitrides can be synthesized via a reaction with a carbon and nitrogen source (melamine, urea, cyanamide) and an alkali salt (NaCl, LiCl, KCl). This process generates crystalline carbon nitride structures with alkali ions (Na+, K+, Cs+) accommodated within the carbon nitride units. Among different synthesis alkali salts in literature, NaCl was used to produce highly crystalline carbon nitrides with ordered poly(heptazine imide) (PHI) structures with sodium ions (Na-PHI).3 Prof. Teixeira's group has developed a simple step to exchange these Na+ cations to desirable transitions metals like Ni, Ru, Fe and Pt. Unlike Na+ cations, transitions metals are chemically bonded to N atoms in a carbon nitride structure and cannot be replaced by other elements. Recent results have shown that these single-atoms/PHI are active catalysts in photooxidation reaction, Fe-PHI is especially active being able to oxidize C-H bond into C=O and C-OH. However, other metals such as Ni-PHI displays a milder activity. For example, our Ni-PHI catalyst in the presence of H2O2 can selectively convert cyclohexene into cyclohexene oxide. Herein, we intend to investigate the photoactivity of Ni-PHI catalysts to promote the epoxidation of vegetable oils double bonds with high efficiency. Once its double bonds are converted into epoxide groups, these triglycerides derivatives can be further polymerized (with amines and curing fasteners) leading to partially renewable polymers that could be integrated for aviation uses. (AU)