COVALENT TRIAZINE FRAMEWORKS AS SUPPORT FOR HETEROGENEOUS CATALYSIS Norini Binti Tahir Department of Chemistry Faculty of Sciences Ghent University Dissertation submitted in fulfillment of the requirements for the degree of Doctor of Science: Chemistry June 2019 ii Promoter Prof. dr. Pascal Van Der Voort Members of the Jury Affiliation Prof. dr. Kristof Van Hecke Universiteit Gent Prof. dr. Sammy Verbruggen Universiteit Antwerpen Prof. dr. Gijs Du Laing Universiteit Gent Prof. dr. Laszlo Vincze Universiteit Gent dr. Sven Rogge Universiteit Gent dr. Himanshu S. Jena Universiteit Gent Ghent University Faculty of Sciences Department of Chemistry Krijgslaan 281 S3, B-9000 Ghent, Belgium Tel.: +32-9-264.44.49 Fax.: +32-9-264.49.83 © 2019 Ghent University, Department of Chemistry, COMOC- Center for Ordered Materials, Organometallics & Catalysis, Krijgslaan 281-S3, 9000 Ghent, Belgium This research was funded by Ministry of Higher Education of Malaysia and Universiti Malaysia Sabah Alle rechten voorbehouden. Niets uit deze uitgave mag worden gereproduceerd, opgeslagen in een geautomatiseerd gegevensbestand, of openbaar gemaakt, in enige vorm of op enige wijze, hetzij elektronisch, mechanisch, door print-outs, kopieën, of op welke manier dan ook, zonder voorafgaande schriftelijke toestemming van de uitgever. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without prior permission from the publisher. iv ACKNOWLEDGEMENTS During the time it has taken to complete my PhD, many people have provided support, guidance and encouragement. Thank you to every single person who helped in any way. Without your help, I could not have achieved what I set out to do. First and foremost, I am deeply indebted to my promoter, Prof dr. Pascal Van Der Voort, for the wonderful opportunity for me to join his research group as his PhD student. Thank you for guiding me along the way, inspiring me to work harder and to go after things I did not know if I could accomplish, and for having high expectations. I could not have imagined having a better advisor and mentor for my PhD study. I would like to thank the rest of my thesis committee: Prof. Van Hecke, Prof. Verbruggen, Prof. Du Laing, Prof. Vincze, dr. Rogge and dr. Himanshu, for their insightful comments and suggestions which was of great help to further improve the quality of my thesis. I would like to thank my collaborators, Prof. Van Speybroeck, Prof. Stevens, Prof. Vincze, Prof. De Geyter and Prof. Morent, for their constructive suggestions and invaluable support for data collection and analysis, without whom I could not complete my research. I would like to acknowledge the financial support from the Ministry of Higher Education of Malaysia and Universiti Malaysia Sabah, for my PhD study. I am also grateful to a number of people who sincerely helped me during my time in COMOC. Special thanks go to Prof. dr. Karen Leus, for her patient and hard work helping me out to get to this point. Thank you for all the guidance, advice and support you have given to me throughout my PhD. I could not have accomplished this thesis without you. I extend my sincere thanks to Guangbo Wang, who always helped me with the research and in the lab, and sharing his scientific idea to work together with me. Special mention also goes to Jeroen, my tea-break ‘companion’, to Flore, my gorgeous partner crime, and to Chidharth, for always helping me with everything. I also want to express my gratitude to my colleagues in the department; Tim, Laurens, Dimitri, Anna, Sara and Parviz, Shuna, Xiao, Hui, Jing, Min, the students (Sander, Geert, Andreas, Marion, Florence, Leo and Maxime) and the members of PCN, Script and Nolan research group. Not to forget to the former colleagues of COMOC; Els, Yesid, Sander, Hannes, Judith, Kevin-α and Kevin-β. I have been very fortunate to work with many people, who I have learned a lot from and shared many good times. I am also hugely appreciative to the staff members of S3, Pierre, Kathleen, Katrien, Pat, Bart, Funda, and Tom, who were always on hand to help me out with everything. And also to Tim and Mario, the Glassblowers. i I simply cannot forget the Malaysian friends, past and present, who went through hard times together, cheered me on, and celebrated each accomplishment. Thank you guys! To my family, mama and bapa, and siblings, who have always believed in me and pushed me to be my absolute best. Your support and prayers throughout my PhD journey have been immeasurable, and I know your love and encouragement have made me into the person I am today. Last and not least, I beg forgiveness of all those who have been with me over the course of the years and whose names I failed to mention. Ik hou van jullie allemaal! Norini Tahir Ghent, June 2019 ii ENGLISH SUMMARY Catalysis played an important role in improving our standard of living over the last century. Due to the constant environmental and economic challenges, there is an urgent need to develop a more sustainable and efficient chemical industry by establishing a more efficient application of chemical transformation. Heterogeneous catalysis, in which the catalyst and the reaction mixture are present in a different phase, often displays significant advantages over homogeneous catalysis in terms of sustainability, recyclability, robustness, and separation of catalysts. Catalysis by porous materials has been extensively used for decades and the growth rates appear to increase in scientific research due to the significant concerns regarding environmental sustainability and future energy security. Our aim in this thesis was to develop highly stable and porous Covalent Triazine Frameworks (CTFs) as scaffolds for catalytically active species in synthetic organic chemistry. CTFs have received significant attention as promising candidates to bridge the gap between homogeneous and heterogeneous catalysts due to their extraordinary stability under harsh synthesis and reaction conditions. In Chapter 1, we presented the general introduction of porous organic frameworks (POFs) and their application in heterogeneous catalysis. POFs consist of crystalline covalent organic frameworks (COFs), and amorphous porous organic polymers (POPs) and CTFs. POFs have attracted considerable attention as platform for heterogenizing homogeneous catalysts due to their remarkable properties such as high surface area, microporosity, low density, and physicochemical stability. The versatility of POFs in heterogeneous catalysis can be achieved by introduction of the catalytic functionality via “bottom-up” synthesis or “post-functionalization” strategies. CTFs are a subclass of POFs and are generally synthesized through the trimerization of nitriles via ionothermal conditions. CTFs exhibit high porosity with exceptional stability toward harsh environments compared to other porous organic frameworks. Because of this remarkable behavior, CTFs offer excellent potential in the development of heterogeneous catalysis. In Chapter 2, the utilization of CTFs as an efficient and highly stable support for both nanoparticles and molecular active catalysts is reviewed. This chapter also presents a general introduction to CTFs and their recent synthetic approaches. Chapter 3 focuses on the heterogenization of a [Ir(OMe)(cod)]2 complex by post- modification of a bipyridine-based CTF (bipyCTF). Experiments and computational calculations confirm the anchoring of the Ir(I)-complex to the bipyridine moieties in the framework and indicate a similar coordination environment to that of the homogeneous counterpart. The introduction of the Ir(I)-complex to bipyCTF provides an efficient heterogeneous catalyst for C-H borylation of various aromatic compounds with the presence of B2Pin2 as borylating agent. Heterogeneity test demonstrated the stability and reusability of Ir(I)@bipyCTF catalyst with excellent yield of products. iii A nitrogen-rich containing building blocks not only provides robust binding sites for metal complexes but also contains a Lewis basic functionality. In Chapter 4, a rigid and planar tris-bidentate ligand of 5,6,11,12,17,18-hexaazatrinaphthylene (HATN) was employed for the preparation of highly porous and nitrogen-rich CTFs. HATN-based CTF exhibited a remarkably high BET surface area of ~1700 m2/g. Post-synthetic metalation of HATN-CTF with a Cu(OAc)2.H2O complex creates an efficient heterogeneous catalyst for the Henry reaction of aromatic aldehydes and nitromethane. The high basicity of the HATN-CTF support facilitates the formation of nitronate species during the catalytic cycle, enhances the catalytic activity and produces higher yields. In conclusion, post-functionalization with catalytic active sites have shown significant contributions to this emerging field of CTFs, particularly in organic transformations. Further examining on both their surface support features and their catalytic behavior allow for a broader insight of their development and application in the industry. iv DUTCH SUMMARY Katalysatoren hebben de voorbije eeuw(en) een belangrijk aandeel gehad in het verbeteren van onze levensstandaard. De uitdagingen op milieu- en economisch gebied blijven echter toenemen, en daarom is er nu, meer dan ooit, nood aan de ontwikkeling van een nog efficiëntere en duurzamere chemische industrie, onder andere door een geoptimaliseerde toepassing van chemische synthese. Heterogene katalyse, waarin de katalysator en het reactiemengsel