Selected hidden gems in a career in nanochemistry

The following article is an abbreviated version of the career reflections of Prof. Geoffrey Ozin, in recognition of his 80th Birthday, to be celebrated at the University of Toronto, Toronto, Canada, on August 23, 2023. Spanning the emergence of nanochemistry to the future of global energy, Prof. Ozin highlights critical junctures and “hidden gem” materials along the way. The following article is an abbreviated version of the career reflections of Prof. Geoffrey Ozin, in recognition of his 80th Birthday, to be celebrated at the University of Toronto, Toronto, Canada, on August 23, 2023. Spanning the emergence of nanochemistry to the future of global energy, Prof. Ozin highlights critical junctures and “hidden gem” materials along the way. A beachcomber, by definition, is “a person who walks along beaches collecting interesting or valuable things, either for pleasure or to sell.” Born in London, England in 1943—with my informative years living in Brighton-by-the-Sea from age 3—as an avid beachcomber, I was familiar with unusual and exciting finds—hidden gems, discovered by chance. Those euphoric days of searching for buried treasures with a metal detector would serve as a model for the story of my academic research career, in a field I fathered and named “nanochemistry”—a bottom-up chemical approach to the synthesis of nanomaterials (Figure 1). Looking back more than half a century, I wondered if it was the exhilaration of a lucky strike that motivated my continuous search for more strikes—more hidden gems at the nanoscale—or a more sophisticated endeavor stirred by wanting to delve deeply into the origin, character, purpose, usage, and value of rare finds. Taking a trip down memory lane, this article documents career highlights and recollections, along with a few discovered gems in a field that is now called nanochemistry. More contemporary at the time, Richard Feynman’s prescient 1959 Caltech lecture, “There’s Plenty of Room at the Bottom,” inspired me—as a new assistant professor arriving in the chemistry department at the University of Toronto in the summer of 1969—to address the challenge of making materials with atom perfect nanoscale dimensions using a bottom-up chemistry approach. If possible, the dream was to study the size-tunable chemical and physical properties of these materials having physical dimensions in the quantum size regime of around 1 nm–100 nm with an eye to elucidating structure, property, function relations, and to ultimately determine their utility in a number of perceived applications that would benefit from what I call the “nano advantage.” My first eureka moment arose by performing chemistry with “naked” metal atoms under cryogenic conditions, where chemical reactions could literally be stopped in their tracks. This revelation opened my mind to the tantalizing possibility that one could control and spectroscopically observe nucleation and growth processes of metal atoms in the absence and presence of small molecules like CO, N2, O2, and C2H4, one atom at a time, to form atom-precise metal nanoclusters. This scientifically exciting feat had never been accomplished before.1Ozin G.A. Vander Voet A. Transition metal atom inorganic synthesis in matrixes.Accounts of Chemical Research. 1973; 6 (Ozin, G. A. (1977). Metal atom matrix chemistry. Correlation of bonding with chemisorbed molecules. Accounts of Chemical Research, 10, 21–26): 313-318Crossref Scopus (55) Google Scholar Today, single-metal-atom catalysis and photocatalysis is a hot topic—what prescience! One of my favorite early initiatives, undertaken while working as a Fairchild Fellow at Caltech in 1977 with William Goddard, was an experimental and theoretical study of Nin(C2H4)m. This work described for the first time the chemistry of naked nickel atoms and nickel clusters with ethylene, envisioning them as a localized bonding model for ethylene chemisorbed on bulk nickel.2Ozin G.A. Power W.J. Upton T.H. Goddard III, W.A. Experimental and theoretical studies of Nin(C2H4)m. Synthesis, vibrational and electronic spectra, and generalized valence bond-configuration interaction studies. The metal atom chemistry and a localized bonding model for ethylene chemisorbed on bulk nickel.J. Am. Chem. Soc. 1978; 100: 4750-4760Google Scholar The ingenuity behind these 1970’s experiments unveiled an unprecedented view of controlled size metal nanoclusters, the synthesis and study of which enabled the first explorations of the transition from molecular to quantum confined to bulk forms of metals. My desire to take the insights gained from this phase of my nanochemistry work on naked metal atom and naked metal cluster chemistry, “out of the cold,” provided the link between my early work and the field of zeolite materials science. I envisioned making and stabilizing these tiny pieces of matter on solid supports so that detailed studies of their structure, property, function, and utility relations could be undertaken. In this context, it occurred to me that, because these Mn and MnLm nanoclusters were inherently metastable with respect to agglomeration to thermodynamically stable bulk materials, they had to be stabilized by some kind of surface-protecting sheath. To this end, I performed the nucleation and growth reactions within the nanometer-sized voids of zeolites, “capping and trapping” the nanoclusters in what I termed a “zeolate” ligand cage.3Ozin G.A. The zeolate ligand: From hydrolysis to capped semiconductor nanoclusters.Adv. Mater. 1994; 6: 71-76Crossref Scopus (35) Google Scholar This work confirmed that zeolites could serve as nanoporous hosts for synthesizing, ligating, and stabilizing metal and semiconductor nanomaterials. During this period, thinking within the zeolite community focused solely on the properties and applications of zeolites in catalysis, ion exchange, and gas separation. However, I preferred to look at zeolites as solids filled with periodic arrays of nanoscale voids and wondered how they could perform and compete in the advanced materials research space. I saw their potential as information storage, photovoltaics, batteries, fuel cells, photocatalysis, chemical sensors, optoelectronics, and drug delivery systems. Exploring this idea, I worked with Edith Flanigen and a team of scientists at Union Carbide in Tarrytown, New York for five years to bring some of these ideas to practice, ultimately describing a vision for the future direction of the field in our paper “Advanced Zeolite Materials Science.”4Ozin G.A. Kuperman A. Stein A. Advanced zeolite materials science.Angew. Chem. Int. Ed. 1989; 28: 359-376Crossref Scopus (361) Google Scholar Zeolite’s limited void space impeded my quest to study nanomaterials at sizes up to 100 nm. It was only after the 1989 discovery of tunable periodic mesoporous silica materials by Charles Kresge and co-workers at Mobil Research in New Jersey that our work on materials on the scale of 2 nm–100 nm could continue. With this newfound access to 1 nm–100 nm length scales, my ensuing research laid out the essence of a chemical approach to nanomaterials—a futuristic field that I called nanochemistry.5Ozin G.A. Nanochemistry: synthesis in diminishing dimensions.Adv. Mater. 1992; 4: 612-649Crossref Scopus (1374) Google Scholar This paper set the scene for a nanomaterials revolution that continues unabated today. In this paper, I envisioned the novel world of nanochemistry with its 0D dots, 1D wires, 2D layers, and 3D open frames, configurations that surprised, shape- and size-dependent behaviors that startled. With this advance, the field of nanochemistry crystallized, giving birth to an explosion of research and new journals that began to publish nanochemistry research with citation impact factors matching or exceeding those published in the flagship journal of their respective society. These include Nano Letters, ACS Nano, Nature Nanotechnology, Nanoscale, and Small. Chemistry, nanoscience, and nanotechnology were forever united through nanochemistry, evidenced by the astronomical growth of nanochemistry ISI citations since 1992, more than 2M hits on Google, and the creation of numerous global initiatives in academic, industry, government, and defense institutions around research and education in nanochemistry. This work mapped the foundation for much of my research on nanomaterials, which underpinned my “panoscopic” vision of materials self-assembly over all length scales. With these conceptual foundations, a bottom-up paradigm for synthesizing nanoscale materials with nanometer-level command over their size, shape, surface and self-assembly emerged. The potential I saw was breathtaking. It would be possible to produce nanoscale materials—perfect down to the last atom—from inorganic components, with structure-property relations designed to yield new materials characterized by an array of novel behaviors and these materials would have real-world applications. Here are nine such “gems” that have driven (and continue to drive) research directions in the field (Figure 2).1.Biomimetic nanochemistry: The paradigm of learning how to transfer nature’s best materials ideas into the nanochemistry laboratory, inspired my discovery of what I termed “morphosynthesis,” a synthetic analog of morphogenesis, the creation of shapes and patterns in the biological world. In this pristine field at the time, my work focused on controlling and understanding, from the nanometer to micron scale, the growth and form of inorganic materials with striking curved shapes and beautiful surface patterns that exhibited what I termed “natural form.” By natural form, I imply the visual perception of a class of materials with shapes and patterns recognized as being associated with the natural world.6Ozin G.A. Morphogenesis of biomineral and morphosynthesis of biomimetic forms.Accounts of Chemical Research. 1997; 30 (Yang, H., Kuperman, A., Coombs, N., Mamiche-Afara, S., and Ozin, G. A. (1996). Synthesis of oriented films of mesoporous silica on mica. Nature, 379, 703–705): 17-27Crossref Scopus (196) Google Scholar2.Mesoscopic materials: This biomimetic way of thinking about lyotropic liquid crystal template-directed co-assembly of inorganics led to my discovery of periodic mesoporous silica in the form of “oriented thin films” grown at liquid-solid and air-solid interfaces.6Ozin G.A. Morphogenesis of biomineral and morphosynthesis of biomimetic forms.Accounts of Chemical Research. 1997; 30 (Yang, H., Kuperman, A., Coombs, N., Mamiche-Afara, S., and Ozin, G. A. (1996). Synthesis of oriented films of mesoporous silica on mica. Nature, 379, 703–705): 17-27Crossref Scopus (196) Google Scholar These papers inspired a world-wide effort on finding utility for periodic mesoporous silica film in optics, fluidics, microelectronics, chromatography, catalysis, and sensing, to name a few applications.3.Hybrid nanomaterials chemistry: A new class of nanocomposite materials called periodic mesoporous organosilicas (PMOs) were also invented during this phase of my work.7Asefa T. MacLachlan M.J. Coombs N. Ozin G.A. Periodic mesoporous organosilicas with organic groups inside the channel walls.Nature. 1999; 402 (Hatton, B., Landskron, K., Whitnall, W., Perovic, D., and Ozin, G. A. (2005). Past, present, and future of periodic mesoporous organosilicas the PMOs. Accounts of chemical research, 38, 305–312): 867-871Crossref Scopus (1683) Google Scholar This distinctive class of hybrid materials contains bridge-bonded organic molecules integrated into the silica pore walls. The organic moieties included but were not limited to aliphatics, alkenes, aromatics, dendrimers, fullerenes, and polyhedral oligomeric silsesquioxanes.Modern PMOs deliver properties that transcend the sum of their inorganic and organic components and have found widespread application as interlayer dielectrics in microelectronic packaging, chromatography stationary phases, chiral catalysis, dental implants, and drug delivery vehicles.7Asefa T. MacLachlan M.J. Coombs N. Ozin G.A. Periodic mesoporous organosilicas with organic groups inside the channel walls.Nature. 1999; 402 (Hatton, B., Landskron, K., Whitnall, W., Perovic, D., and Ozin, G. A. (2005). Past, present, and future of periodic mesoporous organosilicas the PMOs. Accounts of chemical research, 38, 305–312): 867-871Crossref Scopus (1683) Google Scholar4.Host-guest inclusion chemistry: Using chemical vapor deposition and metal organic vapor deposition within the spatial confines of mesoporous hosts it was discovered how to control the nucleation and growth, stabilization, and protection of size- and shape-controlled quantum-confined semiconductor materials, exemplified by nanometer dimension Si, Ge, Ag, AgCl, CdS, SnS2, MoO3, and WO3.8Ozin G.A. Ozkar S. Prokopowicz R.A. Smart zeolites: new forms of tungsten and molybdenum oxides.Acc. Chem. Res. 1992; 25: 553-560Crossref Scopus (54) Google Scholar This genre of ship-in-a-bottle research inspired work on ligand-stabilized colloidal nanocrystals that underpin some of today’s most promising nanotechnologies, including solar cells and batteries, supercapacitors and fuel cells, medical diagnostics, imaging, and theranostic devices.5.Photonic crystal materials: In the next exciting phase of my research, we discovered how to employ opal-templated disilane chemical vapor deposition to synthesize the world’s first 3D silicon photonic crystal with an omni-directional photonic bandgap operating at optical telecom wavelengths of 1.5 microns. This genre of research inspired the synthesis of photonic crystals with a wide range of compositions that could display the full gamut of “color from structure” as found in the natural world. I also showed how to incorporate functional nanoscale planar defects into photonic crystals and how to implement them as a new class of chemical and biological color sensors.9Blanco A. Chomski E. Grabtchak S. Ibisate M. John S. Leonard S.W. Lopez C. Meseguer F. Miguez H. Mondia J.P. Ozin G.A. Large-scale synthesis of a silicon photonic crystal with a complete three-dimensional bandgap near 1.5 micrometers.Nature. 2000; 405: 437-440Crossref PubMed Scopus (1593) Google Scholar6.Smart mirrors: In a flurry of trendsetting papers, I showed how to synthesize alternating composition light diffracting multi-layers made from a wide range of nanomaterials comprised of main group and transition metal oxides, zeolites, mesoporous materials and clays. These self-assembled 2D photonic crystals, called Bragg mirrors, provided high porosity and large surface area, ion exchange, and molecule size discriminating properties to the constituent layers. This enabled active tuning of the structural color of reflected or transmitted light through chemically and physically induced changes in the thicknesses and/or refractive indices of the constituent layers. It led to the development of a new class of colorimetric sensors and anti-bacteria patches with controlled release and detection capabilities.9Blanco A. Chomski E. Grabtchak S. Ibisate M. John S. Leonard S.W. Lopez C. Meseguer F. Miguez H. Mondia J.P. Ozin G.A. Large-scale synthesis of a silicon photonic crystal with a complete three-dimensional bandgap near 1.5 micrometers.Nature. 2000; 405: 437-440Crossref PubMed Scopus (1593) Google Scholar7.Direct laser writing of photonic bandgap materials: In collaboration with colleagues at the Karlsruhe Institute of Technology, I used this nanofabrication method to invert a DLW polymer template in silica by atomic layer deposition. This enabled a subsequent inversion in silicon by disilane chemical vapor deposition, thereby creating a silicon replica of the original polymer template. Silicon photonic bandgap nanomaterials created by this inventive “double-inversion” method facilitate the development of silicon-based all-optical devices, circuits, and chips with utility in optical telecommunication and computer systems. My group spearheaded a creative extension of this work with single-step DLW on a high refractive index “inorganic” photoresist, arsenic sesquisulphide, or As2S3. The work opened the door to a variety of new photonic bandgap materials and architectures that could be made by DLW without using a sacrificial polymer template.10Wong S. Deubel M. Pérez-Willard F. John S. Ozin G.A. Wegener M. von Freymann G. Direct laser writing of three-dimensional photonic crystals with a complete photonic bandgap in chalcogenide glasses.Adv. Mater. 2006; 18: 265-269Crossref Scopus (228) Google Scholar8.Photonic crystal nanochemistry: My research on photonic crystal nanomaterials enabled the invention of actively tuned “photonic color” systems. These materials have been commercialized by Opalux, a spin-off company that I co-founded in 2006 (www.opalux.com). These technology platforms include full color displays, authentication devices for anti-counterfeiting passports and credit cards, alcohol and tobacco, color sensors for food and water quality control, and pathogen detection.9.Clever new nanochemistry twists: My group was amongst the first to demonstrate chemically powered “nano locomotion.” Our work focused on chemical control of the motion of barcode nanorod motors, whose movement is obtained from the decomposition of hydrogen peroxide into water and oxygen at the catalytic segment. The first experiments were aimed at understanding how nanorod rotors function and controlling their speed.11Ozin G.A. Manners I. Fournier-Bidoz S. Arsenault A. Dream nanomachines.Adv. Mater. 2005; 17 (Mirkovic, T., Foo, M. L., Arsenault, A. C., Fournier-Bidoz, S., Zacharia, N. S., and Ozin, G. A. (2007). Hinged nanorods made using a chemical approach to flexible nanostructures. Nature Nanotechnology, 2, 565–569; Cademartiri, L., and Ozin, G. A. (2009). Ultrathin nanowires—a materials chemistry perspective. Advanced Materials, 21, 1013–1020; Sun, W., Qian, C., Chen, K. K., and Ozin, G. A. (2016). Silicon Nanocrystals: It's Simply a Matter of Size. ChemNanoMat, 2, 847–855): 3011-3018Crossref Scopus (494) Google Scholar Subsequently, our group was also the first to show how to make them flexible by integrating polymer hinges between nanorod segments. This trendsetting research has inspired a veritable “nanomotor industry.” Activity in this field is now burgeoning around the world, fueled by visions that these nanomachines could aid in the removal of pollutants from water and act as drug carriers for targeted cancer therapy. Another twist to emerge from our research was the discovery of ultrathin inorganic nanowires with diameters less than 2 nm. These amazingly thin nanowires look, grow, and behave like organic polymers. Our work on nanowires inspired a flurry of activity around the globe to explore the composition, structure, and functionality of these uniquely thin one-dimensional constructs. We raised an important question about how to expand the utilizations of inorganic materials into the applications enjoyed by organic polymers. The opportunities appeared boundless.11Ozin G.A. Manners I. Fournier-Bidoz S. Arsenault A. Dream nanomachines.Adv. Mater. 2005; 17 (Mirkovic, T., Foo, M. L., Arsenault, A. C., Fournier-Bidoz, S., Zacharia, N. S., and Ozin, G. A. (2007). Hinged nanorods made using a chemical approach to flexible nanostructures. Nature Nanotechnology, 2, 565–569; Cademartiri, L., and Ozin, G. A. (2009). Ultrathin nanowires—a materials chemistry perspective. Advanced Materials, 21, 1013–1020; Sun, W., Qian, C., Chen, K. K., and Ozin, G. A. (2016). Silicon Nanocrystals: It's Simply a Matter of Size. ChemNanoMat, 2, 847–855): 3011-3018Crossref Scopus (494) Google Scholar More lately, a twist is my passion for a greener kind of nanochemistry—one founded on non-toxic silicon. To this end, we successfully endeavored to separate poly-dispersions of quantum-confined silicon nanocrystals into mono-dispersed colloidally-stable fractions with tailored organic surfaces. Our structural manipulation of silicon was the first of its kind since the discovery of silicon nanocrystals more than 30 years ago. The bright photoluminescence of these size-separated silicon nanocrystals enabled determination of their size-dependent absolute quantum yields. These photoluminescence quantum yields were surprisingly high and, as a result, are targeted for a range of non-toxic nanotechnologies that include multi-color light-emitting diodes, biomedical diagnostics, and therapeutics and imaging for detecting and targeting tumors. I believe that the technologies derived from non-toxic nanocrystalline silicon can help alleviate the fear of cytotoxicity associated with the heavy metal chalcogenide and pnictide nanomaterials favored in advanced materials and biomedical nanotechnologies.11Ozin G.A. Manners I. Fournier-Bidoz S. Arsenault A. Dream nanomachines.Adv. Mater. 2005; 17 (Mirkovic, T., Foo, M. L., Arsenault, A. C., Fournier-Bidoz, S., Zacharia, N. S., and Ozin, G. A. (2007). Hinged nanorods made using a chemical approach to flexible nanostructures. Nature Nanotechnology, 2, 565–569; Cademartiri, L., and Ozin, G. A. (2009). Ultrathin nanowires—a materials chemistry perspective. Advanced Materials, 21, 1013–1020; Sun, W., Qian, C., Chen, K. K., and Ozin, G. A. (2016). Silicon Nanocrystals: It's Simply a Matter of Size. ChemNanoMat, 2, 847–855): 3011-3018Crossref Scopus (494) Google Scholar10.Seeing the light: One of the hallmarks of my research is the creative exploitation of the unique properties of regular arrangements of nanopores with dimensions that traverse nanometers to microns. For example, my research on periodic macroporous materials, which I aptly calls “light-scale” materials, has been focused on electrically, thermally, mechanically, and chemically tuned “diffractive color from structure.” This revolutionary concept, mentioned above, forms the basis of a new “photonic color” nanotechnology being introduced as unique manifestations of this nanotechnology to the market. For example, P-Nose is an artificial nose comprised of a simple, cost-effective pixilated array of surface-functionalized nanoporous materials that enable discrimination of different analytes, such as molecules comprising the unique identifiers of different bacteria. Think of the possibilities for medical diagnostics and food- and water quality-control. The genre of nanochemistry research demonstrated above has provided the foundation for the most recent phase of my research on new nanomaterials for enabling a global energy revolution. The vision is based upon the discovery of nanostructured photocatalysts capable of both capturing and converting gaseous CO2 into solar fuels that will replace their fossil fuel counterparts, ameliorate climate change and power our planet for the foreseeable future. Around a decade ago, I founded the University of Toronto solar fuels group, comprised of experimental and theoretical materials chemists and chemical engineers working together to build a materials technology that can simultaneously harness abundant solar energy and capture and reduce gaseous carbon dioxide into fuels and chemical feed stocks, simultaneously addressing issues of energy security and climate change (www.solarfuels.utoronto.ca). Today, the increasing greenhouse gas effect of various kinds of methane emissions is becoming important with respect to its effect on climate change, so I thought a lay-level book on “The Story of CH4: Five Atoms that Changed the World,” with graduate student and co-author Jessica Ye, was an informative, important, and timely message for society at large to grasp (Figure 3A). The big picture of greenhouse gas CO2—past, present, and future—has been told in our recently published lay-level book, “The Story of CO2: Big Ideas for a Small Molecule,” co-authored with my graduate student at the time, Mireille Ghoussoub (Figure 3B). With an earth abundant, non-toxic, cost effective, scalable catalyst integrated with existing chemical and petrochemical industrial infrastructure, one can begin to appreciate that CO2 conversion rates of this magnitude can provide a potentially practical, economical, and sustainable alternative to burning and depleting fossil fuel reserves. My vision for an energy transition from one based on unsustainable fossil fuels to a sustainable solar fuels energy technology founded on capturing and utilizing CO2—from both thin air and more concentrated localized sources—is compatible with existing CO2 emitting industries around the world. To achieve this vision of a carbon-neutral air-to-fuel carbon-cycle technology, my group is currently developing compact, tandem, solar-powered photochemical reactors for efficiently splitting gaseous water first into H2 and then using the H2 to reduce gaseous CO2 to fuels and chemicals. I believe the time it should take to convert solar fuels laboratory-scale science to a global technology could be short enough to circumvent the predicted adverse consequences of greenhouse gas climate change, enabling a timely energy transition from fossil fuels to solar fuels. Most recently, the work of my group has been recognized for their fundamental and applied contributions to enabling the energy transition though innovative forms of CO2 management. Our energy materials discovery research for a sustainable future focuses on the development of high-efficiency photocatalysts and photoreactors that enable the greenhouse gas CO2 to be converted into sustainable commodity chemicals and fuels using sunlight, toward the vision of the solar CO2 refinery. The big picture of the energy transition—past, present, and future—has been told in our recently published book, “Energy Materials Discovery: Enabling a Sustainable Future,” co-authored with my post-doctoral coworker at the time, Joel Lohr (Figure 3C). To amplify, the objectives of the last decade of our research is recycling captured CO2 emissions to make sustainable commodity chemicals and fuels. We believe this is a viable strategy for decarbonizing fossil chemical and petrochemical processes. The goal is to use sunlight as a source of renewable energy to drive these CO2 recycling operations to reduce dependency on fossil and electrical energy now used to power energy and carbon-intensive thermochemistry and electrochemistry CO2 utilization processes. This genre of research takes five main field-advancing directions: (1) materials engineering strategies and new reactor designs for enhanced performance heterogeneous CO2 photocatalysis; (2) computational modeling system development strategies for studying the function of defects, photothermal light, and heat in CO2 photocatalysis; (3) overcoming intermittency challenges in photocatalytic CO2 hydrogenation processes using super-capacitive charge-storage materials for 24/7 operations; (4) comparison of thermochemical, photochemical and photothermal CO2 utilization and future opportunities; and (5) key process design engineering technoeconomic and life cycle analysis decision-making criteria for assessing photocatalytic process viability and potential (https://fuelcellsworks.com/news/energy-transition-with-hydrogen-from-the-roof/). Inspired by the vision of solar CO2 refineries, we have enhanced and enriched our understanding of gas-phase heterogeneous CO2 photocatalysis, while facilitating advancements in innovative opto-chemical engineering of high efficiency photocatalysts and photoreactors to realize our dream.12Ozin G. Accelerated optochemical engineering solutions to CO2 photocatalysis for a sustainable future.Matter. 2022; 5 (Kant, P., Liang, S., Rubin, M., Ozin, G. A., and Dittmeyer, R. (2023). Kant, P., Trinkies, L. L., Gensior, N., Fischer, D., et al. (2023). Isophotonic reactor for the precise determination of quantum yields in gas, liquid, and multi-phase photoreactions. Chemical Engineering Journal, 452, 139204; Low-cost photoreactors for highly photon/energy-efficient solar-driven synthesis. Joule, 7, 1347–1362): 2594-2614Abstract Full Text Full Text PDF Scopus (14) Google Scholar Novel photocatalyst architectures integrated with photoreactor designs developed in our research enable accurate determination of key performance metrics, quantum yields and light transport efficiency. The industrial viability of solar chemicals and fuels made from CO2 is assessed by photon-to-product and carbon footprint technoeconomic analyses of the process. This is pivotal groundwork for up-scaling and industrialization of gas-phase heterogeneous CO2 photocatalysis, the mandate of a company I co-founded (www.solistra.ca). Together, with a group of university and international collaborators, I have recently focused my sights on direct air carbon capture (DAC) technology integrated into specially designed freight railcars that are powered by on-board regenerative braking energy. This mobile-DAC technology has the potential to harvest exceptionally large quantities of CO2. Projected to be significantly more energy efficient and cost effective than stationary-DAC technologies, with an annual CO2 sequestration capacity of approximately 4 gigatons by 2050 and 10 gigatons by 2075, it promises to break the $50/tCO2 economic barrier, Figure 3D. A spin-off company has received first round funding to build and test a proof-of-concept DAC train demonstrator (www.Co2Rail.com). I believe that integration of direct air capture and heterogeneous CO2 photocatalysis of the type under current development will enable the manufacture of eco-friendly commodity chemicals and fuels, facilitate decarbonization of fossil chemical and petrochemical industries, reduce atmospheric CO2, and lessen associated healthcare and climate-change costs – all seen as profound socioeconomic benefits if reduced to practice at scale, efficiently and with an economically viable dollar cost of a mole of photons with respect to a mole of product. Nanomaterials are at the beginning of the food chain for diverse advanced materials and biomedical technologies. Without nanochemistry none of our current work aimed at industrialization of CO2 photocatalysis would be possible. The future of this endeavor requires optimization of photocatalyst quantum yield and photoreactor radiation transport efficiency through creative photon capture strategies. I am unabashedly proud of our most recent research, a burst of creativity and energy from a group of talented up-and-coming young scientists who have pioneered a new field we dub “opto-chemical engineering of high efficiency photocatalysts and photoreactors” (Figure 3E). Their work has demonstrated these objectives are achievable by minimizing parasitic light losses to achieve the highest efficiency photon-to-product performance metrics recorded to date.12Ozin G. Accelerated optochemical engineering solutions to CO2 photocatalysis for a sustainable future.Matter. 2022; 5 (Kant, P., Liang, S., Rubin, M., Ozin, G. A., and Dittmeyer, R. (2023). Kant, P., Trinkies, L. L., Gensior, N., Fischer, D., et al. (2023). Isophotonic reactor for the precise determination of quantum yields in gas, liquid, and multi-phase photoreactions. Chemical Engineering Journal, 452, 139204; Low-cost photoreactors for highly photon/energy-efficient solar-driven synthesis. Joule, 7, 1347–1362): 2594-2614Abstract Full Text Full Text PDF Scopus (14) Google Scholar It is tremendously satisfying that, together with my students, our contributions to fundamental research over the past 50 years laid the essence of a chemical approach to nanomaterials, defining the conceptual foundations and securing credibility for a novel scientific discipline. I am thrilled by the way that this new discipline of nanochemistry has developed and matured since my work in the early 70’s, before nanochemistry existed as a field, and continues to serve as an integral driver of further developments in many tangential scientific undertakings, which we now count upon to catalyze scientific, industrial, economic, environmental, and societal advancement. Of course, none of my discoveries in the field of nanochemistry would have been possible without the incredible contributions of a large cadre of exceptionally creative coworkers, almost 70 of whom have gone on to academic positions in top notch universities, scientific positions in national laboratories and chemical industries, and have founded spin-off companies around the world. The recognition of my career’s work in this exciting and developing discipline by my global cadre of alumni and colleagues, on the occasion of my 80th birthday is deeply treasured. For an extended text of these reflections, with additional hidden gems and insights, see www.solarfuels.utoronto.ca. The authors declare no competing interests.