Impact Objectives• Explore synthesising bioactive organic
compounds in a greener fashion• Develop novel reductive systems to tackle
challenging upcycling transformations of highly
oxidised or oxygenated compounds

A catalyst for change
Professor Susumu Saito shares how his work has progressed into groundbreaking research involving a
prototypical structure with the potential to make significant contributions to renewability
What inspired you to
become involved inorganic chemistry?
When I was a highschool student, I
was fascinated tolearn that many medicines are made ofcomplex but beautifully arranged organic
frameworks. My father told me aboutprominent scientists Professor Ryoji Noyori
and Professor Hisashi Yamamoto, bothfrom Nagoya University, who are leadersin the field of organic chemistry in Japan.
My father’s friend, Professor Kohei Tamao,
who won the Frederic Stanley KippingAward in Silicon Chemistry in 2002,
strongly recommended I study organic
chemistry at Nagoya University. When I
was an undergraduate freshman student
at the University, Professor Yamamoto wasteaching a class lecturing on prostaglandins
and their biological functions. I joinedand enjoyed the class, where I becameinterested in synthesising bioactive organiccompounds in an asymmetric fashion.
Can you discuss your work in the design andsynthesis of unknown organic compounds
and molecular catalysts?
Renewable carbon feedstock, including
biomass, carbon dioxide, wasteful plastics,
etc., exist in high oxidation and/or highly
oxygenated states, and thus, current
state-of-the-art oxidation catalysts mustbe substantially modified to achieve thereduction (and dehydration) of such bio-renewable resources. We are developing
tailored molecular (PNNP)M catalysts(PNNP = tetradentate ligand consistingof two-nitrogen and two-phosphine
coordinative atoms, M = metal) that are
responsive to diverse energies (heat, photoand electric), for the reduction of highly
oxygenated/oxidised renewable carbon
feedstock (biomass, CO2, wasteful plastics,etc.) to create energy-rich useful fuels/chemicals focused on the carbon-neutral
social system.
What is the anticipated impact of your work?
Our prototypical structure, (PNNP)M, could
operate as a reduction catalyst responsive
to diverse energies. The novel molecular
design of our (PNNP)M catalysts wasoriginally devised by us, and the reduction
catalyst derived therefrom is highly robust
and its catalytic activity could be sustained
for a long period of time (at least not lessthan 144 h) under both visible light and heat
energy (~200°C). Additionally, the structuralrobustness and high catalytic activity of(PNNP)M catalysts are a prerequisite for
future implementation in society.
How important is collaboration for yourwork?
One of my collaborators is inventing a newwave of Raman spectroscopy techniques.
This short-time resolution (ps~fs: picosecond~femto second) system provides
an unprecedented operando analysis (thiscombines the spectroscopic characterisationof a catalytic material during reaction
with the simultaneous measurement ofcatalytic activity) that could give profoundinsights into ultra-short reaction steps
or courses. Signals of different static anddynamic behaviours of different hydrogenbonds involving water and alcohols could
be separated. Signals of many different
real time reacting C-H bonds may also beseparated. We have the potential to be able
to see more effectively such short-timechemical events spectroscopically using acombination of lasers and Induced Raman
measurements.
Have you had any exciting discoveries?
I am proud of the discovery of the amazing
robustness of (PNNP)M complexes.
We clearly demonstrated a prototypicalmolecular framework (PNNP)M that canbe used as many distinct catalysts overdifferent energy inputs including heat,
light and electric energies while keeping its
robust structure, tetradentate complexation.
Furthermore, when we found (PNNP)Ru
complexes that catalysed effectivehydrogenation of inactivated amides
including nylons, this was a real lightbulb
moment. I was confident with this discovery
that (PNNP)M frameworks could be applied
to many different systems for the reductionof biorenewable carbon feedstock and CO2
to alcohols and of wasteful commodity
plastics to monomer units, as well as
the reduction of side chains with esters/
amides/nitriles of polymers, which havebeen sequentially demonstrated up to date.
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A machine can do better than a human for the discovery of a new photocatalysis?

Sustainable societies builtwith catalysts
The Saito Research Group, Nagoya University, is taking a range of novel approaches to create greener
societies through using catalysis to convert biomass, CO2 and wasteful plastics

In the race towards a more sustainable
future in which fossil fuels are replaced withrenewable energy sources, biorenewableenergy is an exciting concept that holds
great potential for a greener tomorrow.
Biorenewable resources, also known asbiomass, are organic materials such as living
and waste plant matter and animal matterand waste products. These organic materials
can be used to generate electricity andgas in the form of bioenergy. But to makethis bioenergy truly effective and efficient,catalysis is required to convert the biomass
into its useful form. Professor Susumu
Saito heads up the Saito Research Groupin the Noyori Laboratory at the Graduate
School of Science, Nagoya University inJapan, where research is underway to design
catalysts that can facilitate such moleculartransformations.
In one project, the researchers aredeveloping upcycling catalysts for highly
oxidised chemical compounds. Saito
explains that vast quantities of carbon
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dioxide (CO2) are produced every year,
posing significant issues when it comesto achieving a carbon-neutral society.
‘Game-changing catalysts are required tochemically transform those highly oxidisedor oxygenated compounds (HOCs) which
are thermodynamically and kinetically highly
stable,’ he describes. ‘We develop novel
reductive systems involving hydrogen (H2)and H2O as hydrogen and electron sources
for tackling those extremely challenging
upcycling transformations of HOCs.’ The
goal is that using these catalysts makes it
possible to quickly and efficiently synthesise
high-value-added organic moleculesfrom carbon resources. This research
could be transformative in regards to thedevelopment of self-degradable (selfimmolative) plastics and therefore has
great potential to contribute to advancing
sustainable societies.
MAGNIFICENT METAL CATALYSISIn another study, Saito and the team are
exploring organic synthesis based on

one electron transfer from H2 or H2O
using molecular and semiconductor
photocatalysis. ‘Visible light energy can
induce photo-excited states of tailoredhomogeneous and heterogeneous catalysts
which promote the homolytic cleavage ofchemical bonds of H2 or H2O, which gives
very active one electron (radical) species(OES) such as hydrogen atom (H•) andhydroxyl radical (HO•),’ highlights Saito.
‘Using these OESs in addition reactionsand H-abstraction reactions, carboncentred radical species could be readily
generated, by which we will achieve artificial
photosynthesis directed toward selective
organic synthesis (APOS).’An important focus for the researchers is
on molecular metal catalysis. ‘Many people
have an impression that organic molecules
or materials are vulnerable and can be easily
decomposed upon exposure for a while
to light and high temperatures (>200°C),’
observes Saito. ‘For example, pigments thatcolour your hair decompose gradually undersunlight, and their original colour fades.
Historically heterogeneous commercialised
systems involving solid catalysts for CO2
reduction typically operate at temperatureshigher than 240°C but molecular catalysts
frequently degrade and deactivate undersimilar conditions,’ he says. They designed
novel (PNNP)M catalysts, with the M
representing metals, and were able to derivefrom these robust reduction catalysts withcatalytic activity that can be sustained fora long period of time under visible light,
electric and heat energy.

the SDGs including carbon-neutral
systems for energy and resources, CO2reducing systems, and changeover of thepresent polymer-based materials society,all should need much longer-term efforts
and dedication,’ highlights Saito. ‘I havethree young staff in my research groupcollaborating with me, offering them chances
to independently steer on-site managementof experiments and education of students. I
give them big blueprints on steering strategy
for research and which direction we shouldgo in. I also partially support their research

Different ways of thinking, and diverse skills andknowledge, when they are tangible, hit and fuse with
one another, resulting in unexpected novel ideas andunpredictable outcomes
EVOLVING RESEARCH
The team’s focus is now evolving. ‘Chemicaland physical interactions of CO2 withtransition metal complexes (in our cases,hydrogen bonds are provided by the metal
complexes additionally to stabilise transitionstates) or organic compounds in a diverse
fashion,’ outlines Saito. ‘The interactions
by which CO2 is activated are important
to convert CO2 into valuable/energeticallyricher substances, which are more useful.
Additionally, our interest is now moving overto the multiple interactions of nH2O (n = anynumber) and semiconductor surface thatare responsible for sequentially generatingHO• from nH2O and H abstraction fromC-H bonds by HO•, which subsequently
produces a carbon-centred radical for C-C
bond formation reactions.’
Looking ahead, the team has exciting plansin the pipeline, including improving theircurrent state-of-the-art reduction catalysts.
‘We want to transform them into the utmost
point of robust catalyst systems that haveenough potential to be implemented bycollaborating industry sectors,’ says Saito.
Another future line of investigation concerns
their work with (PNNP)M. ‘We plan to
improve the (PNNP)M complexes to makethem adaptable to a more effective polymer
degradation and polymer functional groupconversion.’
CONTRIBUTIONS TO
FUTURE SUSTAINABILITY
Saito is also passionate about supporting
young researchers in his field, particularly
given the need for future generations totake the sustainability baton. ‘To achievefinancially.’ He says that the provision ofmultifaceted opportunities and resources forearly-stage researchers to help them jump
into new or interdisciplinary fields is among
the most important.
Key to the researchers’ success isinterdisciplinary collaboration. ‘Different
ways of thinking, and diverse skills andknowledge, when they are tangible, hit
and fuse with one another, resulting in
unexpected novel ideas and unpredictableoutcomes,’ Saito enthuses. He has many
academic collaborators, including different
theoreticians who are good at inventing newalgorithms, and the quantum calculationof both ground-states and excited states(TD-DFT) of organic molecules, a surface
physicist, experts in machine learning, anda polymer chemist and physicist. ‘They
always bring me new wisdom and value
in research and practical techniques,’ hesays. In addition, collaborators within
industry are an important part of his work.
‘Our collaborators are interested in the
Sustainable Development Goals (SDGs)
through their contribution to the future ofsociety, so we are always talking about how
my innovative results could be embedded
into their originally developed systems andfurther implemented in industry.’ lProject Insights
FUNDING• Ministry of Education, Culture,Sports, Science and Technology, Japan• Japan Society for the Promotion ofScience • Japan Science and Technology
Cooperation • Asashi Glass Foundation
COLLABORATORSDr Takeshi Morikawa (Toyota Central
Research Development & Laboratory),
Associate Professor Yoshihito Shiota(Kyushu University), Professor Takeshi
Yanai (Nagoya University), Dr Akira Yada(National Institute of Advanced Industrial
Science & Technology), Dr Mineto
Uchiyama (Nagoya University), Associate
Professor Toshiki Sugimoto (Institute forMolecular Science), Professor Olga Garcia
Mancheño (University of Münster),
Professor Kazunari Domen (TheUniversity of Tokyo), Professor Takashi
Hisatomi (Shinshu University), ProfessorTakashi Ooi (Nagoya University)
TEAM MEMBERS
Nagoya University - Lecturer Dr Jieun Jung,Assistant Professor Naoki Noto,Assistant Professor Shogo Mori
CONTACT
Professor Susumu Saito
T: +81 52 789 5945
E: saito.susumu.c4@f.mail.nagoya-u.
ac.jp
W: https://noy.chem.nagoya-u.ac.jp/
noy_e/
BIO
Professor Susumu Saito has worked as a
Visiting Researcher at Harvard, USA andbeen at Nagoya University since 1995. He
is an ACP Lecturer awarded from Chinaand Taiwan.

Chopping off the C=O of CO2H by Ru and Re catalysts’swords
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