Preface

We would like to acknowledge all the hard work done during the last year in which the COVID-19 pandemic has altered all our lives. In particular, we would like to dedicate this book to Chia-Kuang (Frank) Tsung and to all those we have lost. Frank passed untimely during the production of this book, and part of his contribution to science will be remembered through this publication.

Confined spaces defined by molecular species have been a primary focus of supramolecular chemistry research since its beginnings in the last century. With the realisation that host–guest chemistry plays a significant role in biological catalysis and molecular conversions by enzymes, supramolecular research has strived to mimic biology by creating reactivity within these confined spaces. This book and its many varied chapters aim to bring together the current state of the art in the understanding, design, characterisation and application of the versatile range of chemically confined spaces, as well as the enhanced reactivity that can be enacted within such spaces by using supramolecular chemistry.

It has been a great pleasure putting this body of work together with a friendly, constructive and varied research community to address the questions: why confined spaces and their relation to host–guest chemistry and reactivity? Diversity in the field is one particular reason why we felt this book needed to be put together. The subject is covered by researchers looking at almost all aspects of reactivity and different types of confined spaces, and just a few examples of its importance can be highlighted by enzymes (both synthetic and natural) and their biology, catalytic processes in industrial conversions of feedstock chemicals (e.g. zeolites), porous materials including porous polymers and metal–organic frameworks (MOFs) and supramolecular chemists working on all classes of materials. Thus the book aims to provide a resource of knowledge, data and information, allowing for experienced and new scientists to tackle applications and novel science surrounding reactivity in confined spaces while providing a conduit to combine a number of separated studies that are closely related but not often, if at all, collated in the same book, journal, conference or grouping of scientific subjects. In general, the book covers supramolecular catalysis, a subject that has not had a clear review or dedicated book in over a decade and that has developed substantially in that time. We combine classical host–guest chemistry with catalysis, reactivity and modern supramolecular chemistry, alongside the different technologies to describe and understand reactivity in confined spaces, in one accessible title.

The book consists of 14 chapters which have been written by a broad spectrum of expertise and which we hope will guide the reader from the solution to the solid-state. We start the book with Nick Evans’ excellent take on classical host–guest chemistry of organic macrocycles and the reactivity within the modern technological marvel of catenanes and rotaxanes. We then move into the use of molecular cages, both coordination-based and organic in nature, in Chapters 2–6. The first of these chapters, by Rebecca Spicer and Paul Lusby, develops the differing strategies towards catalysis within coordination cage structures. Photochemistry, with its importance epitomised by photosynthesis, is covered in depth by the chapter titled “Photoreactions in Cages” by Thomas Comerford, Eli Zysman-Colman and Michael D. Ward. Confined spaces can be used to not only enable reactivity but also retard it, and the chapter from Jonathan Robson and Imogen Riddell provides a description of the process of “Stabilising Reactive Intermediates in Cages”. Following these chapters on coordination cage chemistry and the reactivity within their confined spaces, the reader is introduced to confined spaces defined by organic-based chemistries. Carmine Gaeta, Carmen Talotta, Margherita De Rosa, Pellegrino La Manna, Annunziata Soriente and Placido Neri introduce “Reactivity in Self-Assembled Organic Hosts” through describing the chemical reactivity with the hexameric resorcinarene capsule(s). Giuseppe Borsato, Fabrizio Fabris and Alessandro Scarso continue this organic host storyline by discussing “Properties and Reactivities of Coordination Metal Complexes within Organic Nanocontainers”. Moving on from discrete molecules, the remainder of the chapters are focussed primarily on utilising confined spaces within materials to induce chemical reactivity. The first covers reactivity within the confined spaces at the interface of solids and solutions in the form of a chapter on “Reactivity on and within Supramolecular Gels”. As editors, one of our aims for the book was to provide a conduit for the realisation that many of the concepts of controlling reactivity in confined spaces are applicable across all fields researching it. The next chapter by Sonja Pullen and Guido Clever emphasises this best, describing “Catalysis in Confined Space – Relationship between Metal-Organic Frameworks and Discrete Coordination Cages”. Hellen Videa and Antonio J. Martínez-Martínez then give us a treatise on the “Solid/Gas Reactivity of Organometallic Species in Confined Spaces”, which highlights how crystalline molecular materials have incredibly rich chemistry and so can no longer be viewed as “cemeteries for molecules”. When discussing reactivity in molecular crystalline materials, we cannot leave out topochemistry. Gonzalo Campillo-Alvarado, Changan Li and Leonard R. MacGillivray show how “topochemistry meets supramolecular chemistry” and how it can be viewed as “opportunities for targeted organic synthesis in molecular crystals”. The final four chapters cover the highly important research field of reactivity in the confined spaces of porous crystalline materials. Starting with the contribution from Sarah L. Griffin, Georgia Orton, Rosemary J. Young, Christopher J. Sumby, Christian J. Doonan and Neil R. Champness, who describe “Stabilising and Characterising Homogeneous Catalysts in MOFs”, we return to the mimicking of natural processes in the chapter by Xiaoliang Wang and Shengqian Ma titled “Biomimetic Metal–organic Frameworks: Construction and Catalytic Performance”. The final two chapters cover the use of reactive metal species confined within the voids of metal–organic frameworks. Firstly, James King and Petra Á. Szilágyi write about “Catalytic Nanoparticles in Metal–organic Frameworks”. Finally, Donatella Armentano and Emilio Pardo describe “Atomically Precise Metal Clusters in Confined Spaces of Metal–Organic Frameworks”. The book's journey from discrete molecules to self-assembled polymeric structures, covering organic, inorganic and hybrid materials chemistries, affirms our belief in the broad applicability of confined spaces, in all shapes and forms, to facilitate catalysis and chemical reactivity.

Acknowledgements are incredibly important as they indicate how significant the amount of peoples’ effort it has taken for a production like this book. We are hugely grateful for the contributions of several people who have significantly helped to put this book together. Firstly, we would like to thank Jon Steed and Phil Gale who brought us, as editors, this opportunity and provided us with some well used advice. The invaluable support and experience from the Royal Society of Chemistry team of Robin Driscoll, Connor Sheppard, Katie Morrey, Lewis Pearce and the book production division at the Royal Society of Chemistry allowed all involved to produce this significant piece of work during what can only be described as a difficult year. We enlisted a diverse set of researchers from around the world to help review the scientific content of the book. We therefore acknowledge (alphabetically) and gratefully thank Pablo Ballester (Institut Català d'Investigació Química, Spain), Paul Beer (University of Oxford, UK), Susan Bourne (University of Cape Town, South Africa), Tendai Gadzikwa (Kansas State University, USA), Cally Haynes (University College London, UK), Hai-Long Jiang (University of Science and Technology of China, China), Jonathan Nitschke (University of Cambridge, UK), David Smith (University of York, UK), Shane Telfer (Massey University, New Zealand), Frank Tsung (Boston College, USA), David Turner (Monash University, Australia), J. J. Vittal (National University of Singapore, Singapore), Casey Wade (The Ohio State University, USA) and You-Quan Zhou (University of Cambridge, UK).

Ross S. Forgan and Gareth O. Lloyd