Novel nanocatalysts for sustainable chemical processes

The sustainability of chemical processes plays a critical role today, driven by the growing awareness of climate change, energy demands, and environmental challenges caused by human activities. Heterogeneous catalysis plays a crucial role in addressing these issues: the use of a catalyst allows the reduction of process energy consumption, simultaneously guiding the reactions towards the desired product, decreasing waste and byproducts. Moreover, the heterogeneous nature of the catalysts facilitates their recovery and reuse across multiple cycles, further minimizing the production of catalyst-derived waste. Thus, from this perspective, the design of heterogeneous catalysts with tailored structure can increase the efficiency and sustainability of catalytic processes. In this regard, the underlying concept of this thesis is the development of novel, tailored catalysts for practical applications. The focus, in particular, is the synthesis of pharmaceutical intermediates and fine chemicals. These reactions are often conducted under using homogeneous molecular catalyst, with subsequent difficulties in catalyst recycling and reutilization, and the need for external ligands, additives, or co-catalysts. Moreover, for complex organic transformations in liquid phase, harsh reaction conditions in terms of time, temperature, and pressure, are often required. Thus, a helpful approach from this viewpoint can be the development of heterogeneous catalytic processes for fine chemical and pharmaceutical synthesis, retaining not only catalytic performances, but also increasing the sustainability of the processes by lowering waste production and energy consumption. Moreover, heterogeneous catalyst nanostructuring avoids the use of external ligands or additives, furtherly simplifying downstream purification operations, and reducing the waste generated by these external additions. This thesis targets several reactions and presents new catalysts that can drive these processes with greater efficiency, selectivity, and sustainability. For example, the thesis introduces a single-atom copper-based catalyst for diaryl ether synthesis, where the metal is anchored on the support by a polyaminic linker, which acts as a ligand to boost catalytic efficiency. Moreover, a single-site catalyst is proposed for the photocatalytic C-O cross coupling between aryl/alkyl halides and carboxylic acids, where the integration of Ni single atoms in the catalyst generates a sole material capable to undergo simultaneously the photoredox and metallaphotocatalytic cycles. For the photocatalytic trifluoromethylation of heteroaromatic rings, it presents heterogeneous catalyst designed to facilitate material recycling and double system productivity through continuous-flow technology and fixed-bed reactor integration. Beyond these applications, the thesis also explores catalysts for photocatalytic degradation of persistent pollutants, such as Gemfibrozil, emphasizing the generation of non-toxic degradation products. Overall, this work opens new pathways for sustainable chemical production, demonstrating the potential of tailored heterogeneous catalysts for scalable applications in pharmaceutical synthesis and pollution mitigation. Through a combination of computational studies and practical experimentation, this thesis also provides a comprehensive approach to understanding these reactions and solving modern chemical challenges. From this perspective, the development and application of single-atom catalysts tailored for industrial scale applications represents a fundamental goal to achieve, due to the enormous potentialities of this class of catalysts and their growing impact on the academic research. In this sense, the peculiar features of these materials can lead not only to an improvement in the efficiency, but also to a drastic increase of the sustainability of these processes. The sustainability of chemical processes plays a critical role today, driven by the growing awareness of climate change, energy demands, and environmental challenges caused by human activities. Heterogeneous catalysis plays a crucial role in addressing these issues: the use of a catalyst allows the reduction of process energy consumption, simultaneously guiding the reactions towards the desired product, decreasing waste and byproducts. Moreover, the heterogeneous nature of the catalysts facilitates their recovery and reuse across multiple cycles, further minimizing the production of catalyst-derived waste. Thus, from this perspective, the design of heterogeneous catalysts with tailored structure can increase the efficiency and sustainability of catalytic processes. In this regard, the underlying concept of this thesis is the development of novel, tailored catalysts for practical applications. The focus, in particular, is the synthesis of pharmaceutical intermediates and fine chemicals. These reactions are often conducted under using homogeneous molecular catalyst, with subsequent difficulties in catalyst recycling and reutilization, and the need for external ligands, additives, or co-catalysts. Moreover, for complex organic transformations in liquid phase, harsh reaction conditions in terms of time, temperature, and pressure, are often required. Thus, a helpful approach from this viewpoint can be the development of heterogeneous catalytic processes for fine chemical and pharmaceutical synthesis, retaining not only catalytic performances, but also increasing the sustainability of the processes by lowering waste production and energy consumption. Moreover, heterogeneous catalyst nanostructuring avoids the use of external ligands or additives, furtherly simplifying downstream purification operations, and reducing the waste generated by these external additions. This thesis targets several reactions and presents new catalysts that can drive these processes with greater efficiency, selectivity, and sustainability. For example, the thesis introduces a single-atom copper-based catalyst for diaryl ether synthesis, where the metal is anchored on the support by a polyaminic linker, which acts as a ligand to boost catalytic efficiency. Moreover, a single-site catalyst is proposed for the photocatalytic C-O cross coupling between aryl/alkyl halides and carboxylic acids, where the integration of Ni single atoms in the catalyst generates a sole material capable to undergo simultaneously the photoredox and metallaphotocatalytic cycles. For the photocatalytic trifluoromethylation of heteroaromatic rings, it presents heterogeneous catalyst designed to facilitate material recycling and double system productivity through continuous-flow technology and fixed-bed reactor integration. Beyond these applications, the thesis also explores catalysts for photocatalytic degradation of persistent pollutants, such as Gemfibrozil, emphasizing the generation of non-toxic degradation products. Overall, this work opens new pathways for sustainable chemical production, demonstrating the potential of tailored heterogeneous catalysts for scalable applications in pharmaceutical synthesis and pollution mitigation. Through a combination of computational studies and practical experimentation, this thesis also provides a comprehensive approach to understanding these reactions and solving modern chemical challenges. From this perspective, the development and application of single-atom catalysts tailored for industrial scale applications represents a fundamental goal to achieve, due to the enormous potentialities of this class of catalysts and their growing impact on the academic research. In this sense, the peculiar features of these materials can lead not only to an improvement in the efficiency, but also to a drastic increase of the sustainability of these processes.

La sostenibilità dei processi chimici gioca un ruolo fondamentale, direttamente conseguente alle recenti preoccupazioni climatiche, energetiche ed ambientali insorte in seguito all’antropizzazione del mondo conosciuto. Di centrale importanza, in questo contesto, è la funzione della catalisi eterogenea: l’utilizzo di un catalizzatore, infatti, permette di andare a ridurre il consumo energetico del processo, andando contestualmente a reindirizzare la selettività dello stesso verso il prodotto di interesse, diminuendo la produzione di scarti e reflui. Inoltre, la natura eterogenea dei materiali in questione permette un facile recupero e riutilizzo per svariati cicli dei materiali catalitici, ulteriormente diminuendo la produzione di reflui derivanti dal catalizzatore. Quindi, da questo punto di vista, il design dei catalizzatori eterogenei ricopre un ruolo fondamentale, andando ad aumentare l’efficienza e, di conseguenza, la sostenibilità, dei processi catalitici. Da questo punto di vista, l’idea alla base di questa tesi è lo sviluppo di nuovi catalizzatori eterogenei sviluppati su ad hoc per applicazioni di natura pratica. In particolare, l’attenzione è stata posta su reazioni di sintesi farmaceutica e di chimica fine. Queste reazioni sono spesso condotte in presenza di un catalizzatore omogeneo, con conseguenti difficoltà nel recupero e riutilizzo dei catalizzatori, e il bisogno di ligandi, additivi, o co-catalizzatori introdotti esternamente. Inoltre, per reazioni organiche complesse condotte in fase liquida, spesso sono richieste condizioni di reazioni difficoltose dal punto di vista di tempo, temperatura, e pressione. Da questo punto di vista, quindi, una soluzione ottimale può essere lo sviluppo di processi catalitici eterogenei che non solo mantengano l’attività catalitica, ma che vanno ad incrementare la sostenibilità dei processi stessi riducendo il consumo energetico e la produzione di rifiuti. Inoltre, l’utilizzo di catalizzatori eterogenei propriamente nanostrutturati può evitare l’utilizzo di agenti esterni quali ligandi o additivi, ulteriormente facilitando le operazioni di purificazione e riducendo i rifiuti prodotti da queste specie. L'obiettivo di questa tesi è dunque lo sviluppo di nuove reazioni e materiali che possano catalizzare questi processi con migliorata efficienza, selettività e sostenibilità. Ad esempio, questa tesi presenta un catalizzatore eterogeneo per la sintesi di diarileteri, il lavoro proposto presenta un catalizzatore a singolo atomo a base di rame ancorato al supporto tramite un linker poliamminico, che funge da ligando, aumentando le prestazioni catalitiche del materiale. Inoltre, viene proposto un catalizzatore a singolo atomo per il C-O coupling fotocatalitico tra alchil/arilbromuri e acidi carbossilici, dove l’inserimento dei singoli atomi di Ni nel sistema catalitico crea un unico materiale integrato capace di effettuare sia il ciclo fotoossidoriduttivo che quello metallacatalitico. Per la trifluorometilazione fotocatalitica di anelli eteroeromatici, il lavoro presenta un catalizzatore eterogeneo progettato allo scopo di facilitare il riciclo del materiale e raddoppiare la produttività del sistema, integrando la tecnologia a flusso continuo e l’utilizzo di un reattore a letto fisso. Infine, Oltre a queste applicazioni, la tesi esplora anche materiali catalitici per la degradazione fotochimica di inquinanti persistenti, come il Gemfibrozil, andando a sottolineare la generazione di prodotti di degradazione non tossici. Nel complesso, questo lavoro apre nuovi orizzonti per una produzione chimica sostenibile, dimostrando le potenzialità dei catalizzatori eterogenei per applicazioni di sintesi organica e rimozione di inquinanti. Tramite la combinazione di tecniche sperimentali e studi computazionali, questa tesi fornisce un approccio completo, adatto alla comprensione di queste reazioni, risolvendo sfide moderne presentate nel mondo chimico. In particolare, lo sviluppo e l’utilizzo di catalizzatori a singolo atomo su misura per applicazioni di interesse e scala industriale rappresenta un obiettivo fondamentale da raggiungere, data l’enorme potenzialità di questa classe di materiali e il loro impatto sulla ricerca accademica. In questo senso, le loro peculiari caratteristiche possono apportare cospicui miglioramenti non solo nell’efficienza, ma anche nella sostenibilità dei processi scelti.