Sustainable Nanoscale Engineering: From Materials Design to Chemical Processing

Book Preface

Nanotechnology and nanomaterials are among the most significant scientific and industrial research breakthroughs of the 21st century. With the rapid globalization of science, chemists, materials scientists, and chemical engineers are synergistically working together worldwide to understand how to manipulate matter for the benefit of humankind. The Sustainable Development Goals set by the United Nations provide a blueprint through which a thriving and more sustainable future can be achieved for all (Fig. 1.1) [1]. These goals address the global challenges we face, and most of them are directly affected by chemical manufacturing. Consequently, it is our responsibility to design, manufacture and recycle chemicals, and develop processes, considering sustainability. Although there is a lack of consensus on the detailed meaning of the concept [2], sustainable manufacturing, we take here a working definition by the United States’ Environmental Protection Agency (EPA) as the creation of manufactured products through economically sound processes that minimize negative environmental impacts while conserving energy and natural resources [3].

There are several emerging areas of nanoscale engineering with great promise for sustainable chemical engineering. Enzymes, nature’s biocatalysts, have outstanding selectivity and activity and facilitate a broad range of chemical transformations under mild reaction conditions. Besides their natural aqueous environment, there is a need for exploring and exploiting enzymes in organic solvents. The work on directed evolution to engineer enzymes earned the 2018 Nobel Prize in Chemistry for Frances Arnold. Enzymes engineered through directed evolution have great potential in the sustainable processing of a wide variety of chemical products, from pharmaceuticals to biomass. In parallel to the advancement of enzyme catalysis, the field of organocatalysis has emerged. Organocatalytic reactions exploit small-molecule enzyme mimics that are robust, safe, sustainable, metal-free, and scalable [4]. Further developments in the field of catalysis both at nanoscale and process scale are crucial to advancing sustainability because more than 90% of chemical engineering processes utilize catalysts globally [5].

There are a plethora of innovative methodologies, all with the potential to enable sustainable industrial development, on the rise. The World Economic Forum, the International Union of Pure and Applied Chemistry, and the MIT Technology Review have published their own selections of the top 10 emerging technologies improving sustainability [6e8]. The unique advantages offered by flow chemistry and flow reactors have already triggered companies to invest in research and development, pilot scale tests, and implementation in production lines. Solvent-free reactive extrusion for mechanochemical synthesis and 3D printing of advanced engineering materials are emerging fields, with implementation and scale-up challenges yet to be solved. For about half-a-century, there has been a race to develop artificial leaves to efficiently mimic photosynthesis and transforming carbon dioxide into liquid fuel [9,10]. The production of liquefiable hydrocarbons from excess carbon dioxide, water, and other sustainable resources such as sunlight will create new opportunities for energy storage. Despite the tremendous efforts, these ideas are in their infancy, and it is essential that the enabling process development keeps pace with the scientific breakthroughs. Speaking about his startup using hydrogen-producing artificial leaves, Nocera lamented that “I did a holy grail of science. Great! That doesn’t mean I did a holy grail of technology,” [9] highlighting the importance of scale and engineering. Recent breakthroughs in artificial intelligence (AI), in particular deep learning and generative adversarial networks, have allowed machines to mimic imagination (Fig. 1.2), which is a big leap toward unsupervised learning [11]. These advanced methodologies have much to offerscientists and engineers working with largedatabases, albeit suffering fromlimitations such as heavy reliance on quality data. The powerof these advancements in AI can onlybe exploited if research data are reported in a machine-readable manner and managed in online databases accessible to everyone. Most of the research data are mostly reported in image formats, which results in the loss of precise data points. Options for interactive plots are on the rise, and they ought to become mandatory in the near future. There are numerous technical, engineering, and financial challenges associated with developing new, or repurposing conventional and existing, materials and processes to sustainable alternatives. Thanks to the increasing efforts of the industrial sector, in particular the pharmaceutical manufacturers, the “sustainability” buzz word has started to manifest in actions. Several companies have explicitly and publicly started using green chemistry and engineering as key drivers and to innovate around sustainable initiatives. The next subsections and chapter in Sustainable Nanoscale Engineering highlight the sustainability potential of state-of-the-art materials ranging from smart polymers, through 2D materials, to metaleorganic frameworks (MOFs) considering both their fabrication and application (Fig. 1.3). Moreover, the potential of continuous flow processes, lifecycle optimization, and AI directed toward sustainable nanoscale engineering are also evaluated. Besides the direct research and development initiatives aiming at sustainable solutions, it is equally important that we incorporate these initiatives into the chemistry, materials science, and chemical engineering curricula so as to equip our future generations to tackle challenges with a sustainable mindset. Surely, in the not-too-distant future, we will live in a sustainable world enabled by the fascinating materials, processes, and methodologies described in this book.