Susumu Kitagawa

2025 Nobel Laureate in Chemistry
Kyoto University, Japan

Nobel Laureate Public Lecture: From Emptiness to Function – The Philosophy and Chemistry of Molecular Space

For much of human history, empty space was often regarded as the absence of value. In the Western intellectual tradition, Aristotle famously stated that “nature abhors a vacuum,” reflecting a view that completeness and density are associated with perfection. In materials science, this perspective persisted for centuries: solids were expected to be dense, rigid, and unchanging.

Yet some of the most important advances in chemistry have emerged from questioning such assumptions. The development of metal–organic frameworks (MOFs) introduced a fundamentally different concept: empty space within a crystal can be designed, controlled, and transformed into a source of function. These porous crystalline materials contain precisely defined molecular spaces capable of storing, separating, and recognizing molecules with remarkable selectivity. The origins of this research were rooted not in immediate applications but in curiosity-driven exploration of coordination chemistry, at a time when porous crystals were often considered scientifically unimportant. Over time, these studies evolved into a new field of materials science and revealed that molecular space itself can become an active component of function. More recently, the discovery of Soft Porous Crystals has shown that molecular space is not merely static. These materials can adapt, breathe, and respond to guest molecules, demonstrating that order and flexibility can coexist within a crystalline framework. Such behavior challenges traditional notions of matter and suggests new design principles based on responsiveness rather than rigidity.

This lecture explores the scientific journey from “emptiness” to function, highlighting how unconventional ideas can reshape entire fields of research. Beyond the chemistry of MOFs, it reflects on broader questions concerning creativity, curiosity, and the role of fundamental research in generating unexpected innovations. The story of molecular space illustrates how concepts once regarded as useless may ultimately transform the way materials are designed and how society addresses challenges in energy, environment, and health.

Plenary Lecture: Soft Porous Crystals: A New Paradigm in MOF Chemistry

For decades, functional materials have been designed based on the central principle that rigidity defines performance. Dense and stable structures are associated with key properties such as conductivity, magnetism, and mechanical strength, forming the foundation of modern materials science. Within this framework, structural flexibility has generally been viewed as a weakness rather than a source of function. This talk will present a fundamentally different perspective emerging from the study of metal–organic frameworks (MOFs): softness and structural dynamics can themselves generate function. This idea has led to the development of Soft Porous Crystals (SPCs), which are crystalline materials that undergo reversible, stimulus-responsive structural transformations upon interaction with guest molecules. In contrast to traditional porous materials characterized by static architectures, SPCs exhibit dynamic structural adaptations, such as breathing, gate-opening, and framework deformation. In these systems, function is not solely predetermined by structure; rather, it emerges through the interplay between flexibility and molecular recognition. This enables selective adsorption, responsive transport, and tunable interactions with gases and other species. The origins of this paradigm trace back to early studies of coordination polymers, when such materials were not widely regarded as functional. Over time, the ability to design ordered nanospaces gave rise to MOFs as a new materials platform. The discovery of their dynamic behavior challenged the long-standing assumption that crystallinity requires rigidity, demonstrating that order and softness can coexist within a single material system. More recently, the field has begun to evolve toward a fourth generation of MOF-based materials, where hybridization and interface engineering are essential. By integrating SPCs with other materials, dynamic molecular behavior can be translated into macroscopic functionality, opening new opportunities for practical applications. Beyond their fundamental significance, SPCs hold strong potential to address challenges in energy, the environment, and health, particularly through the selective capture and transformation of gas molecules. More broadly, they illustrate how a shift in perspective—from rigidity to adaptability—can redefine the design principles of materials science. I will conclude by discussing how this emerging paradigm of dynamic porous materials may shape the future of chemistry, in which function arises not from static structures but from responsive and adaptive behavior.

Bio:

Kitagawa’s main research field is inorganic and material chemistry, in particular, chemistry of coordination space, and his current research interests are centered on synthesis and properties of porous coordination polymers/metal-organic frameworks.

He was the first to discover and to demonstrate “porosity” for metal complexes with gas sorption experiments (1997), whose materials are called porous coordination polymers (PCPs) or metal-organic frameworks (MOFs). To date, MOFs are classified as a new category of porous materials, as opposed to the conventional classifications of inorganic and carbon materials. Kitagawa pioneered the functional chemistry of MOFs, and discovered flexible MOFs, dissimilar to those of conventional porous materials. Today several hundred different MOFs are known, and over 7,000 articles on this class of materials have been published annually worldwide. The research developments built on his discoveries are anticipated to lead to radical innovations in materials science, with wide-ranging implications for both academia and industry. Chemical industry firms are producing MOF materials for use in purification, storage, and transportation of gases, among other applications. Kitagawa’s achievement has blazed a trail to a new era for porous materials, vital to addressing energy and environmental issues and contributing to human welfare.