HETEROGENEOUS TRANSITION METAL CATALYSTS FOR SUSTAINABLE CHEMISTRY: FROM METAL NANOPARTICLES TO SINGLE ATOM

HETEROGENEOUS CATALYSIS PLAYS A PIVOTAL ROLE IN MODERN CHEMISTRY, FROM THE ACADEMIC RESEARCH TO THE INDUSTRIAL PRODUCTION. THE CATALYTIC PERFORMANCE OF SUPPORTED METAL CATALYSTS STRONGLY DEPENDS ON STRUCTURAL AND ELECTRONIC FACTORS SUCH AS METAL DISPERSION, PARTICLE SIZE, OXIDATION STATE, AND THE NATURE OF THE SUPPORT. UNDERSTANDING AND CONTROLLING THESE PARAMETERS ARE ESSENTIAL FOR THE FINE TUNING OF THE ACTIVITY AND SELECTIVITY OF THE CATALYTIC PROCESSES. THIS PHD THESIS FOCUSES ON THE DESIGN AND APPLICATION OF HETEROGENEOUS TRANSITION METAL CATALYSTS FOR SUSTAINABLE CHEMICAL TRANSFORMATIONS, SUCH AS THE INTRAMOLECULAR HYDROAMINATION OF ALKYNYLANILINES, THE SELECTIVE OXIDATION AND OXIDATIVE ESTERIFICATION OF BIOBASED ALCOHOLS, AND THE DECOMPOSITION OF FORMIC ACID FOR HYDROGEN GENERATION. PARTICULAR ATTENTION HAS BEEN DEVOTED TO ELUCIDATING HOW VARIATIONS OF THE METAL, PARTICLE SIZE, AND NATURE OF THE SUPPORT CAN MODULATE THE CATALYTIC PERFORMANCE. THIS ANALYSIS OFFERS VALUABLE INSIGHT INTO THE STRUCTURE–ACTIVITY RELATIONSHIP AND PROVIDES FOUNDATION FOR THE RATIONAL OPTIMIZATION OF THE CATALYST ENGINEERING. HYDROAMINATION IS AN ATOM-ECONOMICAL STRATEGY FOR CONSTRUCTING N-CONTAINING COMPOUNDS. ITS INTRAMOLECULAR VARIANT PROVIDES ACCESS TO N-HETEROCYCLIC SCAFFOLDS, CORE MOTIFS IN NUMEROUS BIOLOGICALLY ACTIVE MOLECULES, INCLUDING NATURAL ALKALOIDS AND PHARMACEUTICALS. IN THIS THESIS, THE INTRAMOLECULAR HYDROAMINATION OF 2-(2-PHENYL)PROPYNYLANILINE WAS INVESTIGATED USING THE COMMERCIAL AU/TIO2 CATALYST, REVEALING KEY MECHANISTIC INSIGHTS IN WHICH BOTH THE GOLD NANOPARTICLES AND THE OXIDE SUPPORT WERE FOUND TO ACT COOPERATIVELY IN THE CATALYTIC PROCESS, ENABLING EFFICIENT C–N BOND FORMATION EVEN AT LOW TEMPERATURE. OXIDATION REACTIONS ARE A CORNERSTONE OF INDUSTRIAL CHEMISTRY. HOWEVER, THE SELECTIVE OXIDATION OF ALCOHOLS REMAINS A MAJOR CHALLENGE SINCE CONVENTIONAL PROCESSES TYPICALLY RELY ON STRONG OXIDANTS AND HARSH REACTION CONDITIONS. IN THIS WORK, THE OXIDATION OF ALCOHOLS AND BIO-DERIVED 5-HYDROXYMETHYLFURFURAL (HMF) WAS CARRIED OUT UNDER MILD CONDITIONS USING MOLECULAR OXYGEN AS OXIDANT AND GOLD NANOPARTICLES (AUNPS) EMBEDDED IN A POROUS POLYPHENYLENE OXIDE (PPO) MATRIX. THIS STUDY DEMONSTRATES HOW TAILORED SUPPORTS CAN MODULATE THE CATALYTIC MICROENVIRONMENT AND ADDRESS PRODUCT SELECTIVITY. FORMIC ACID (FA) DECOMPOSITION (FAD), A REACTION OF GROWING RELEVANCE FOR HYDROGEN STORAGE AND GENERATION, WAS EXPLORED USING THE AUNPS/PPO CATALYST THAT EXHIBITED REMARKABLE ACTIVITY THEREBY DEMONSTRATING VERSATILITY ACROSS BOTH FINE CHEMICAL SYNTHESIS AND ENERGY-RELATED APPLICATIONS. FINALLY, A NOVEL SINGLE-ATOM NICKEL CATALYST (NI-SAC) SUPPORTED ON A CARBON DOPED MATRIX WAS DEVELOPED AND TESTED IN FAD. NICKEL IS AN EARTH-ABUNDANT ALTERNATIVE TO NOBLE METALS AND HAS RECENTLY EMERGED AS A PROMISING CANDIDATE IN THIS FIELD. HOWEVER, MOST OF THE NISACS SO FAR REPORTED EXHIBITED ONLY LIMITED PERFORMANCE UNDER MILD CONDITIONS AND HIGH FA CONCENTRATION. THE NI-SAC DESCRIBED IN THIS WORK RESULTED STABLE OVER LONG REACTION TIME LEADING TO EXCELLENT RESULTS; MOREOVER, A COMPARISON BETWEEN THE ACTIVITY OF NINPS AND NISAC WAS ALSO POSSIBLE.