Editorial for the Special Issue: Dimensionality of Emerging Materials and Energy

Many emergent materials have shown striking application potential in all fields of energy. Catalytic metal-organic frameworks and photovoltaic hybrid organic-inorganic perovskites are two representative examples. These emergent materials exhibit different structural and quantum degrees of freedom that conventional materials are unable to show. Compounds with similar chemical compositions can often lead to crystal structures with different dimensionalities, and these in turn give rise to distinct electronic and energetic characteristics arising from dimensionality-dependent quantum effects. In addition, their facile synthesis enables artificial control of morphologies in the nano, micro, and bulk forms. This special issue, organized and edited by Profs. Xian-He Bu, Natalia Shustova, and Edward Sargent, focuses on the dimensionality of emerging materials and energy. It includes 24 reviews and 1 perspective. This issue aims to discuss applications of these materials and relative to atomic, electronic, and phononic behavior. The issue includes metal-organic frameworks, covalent-organic frameworks, hybrid organic-inorganic perovskites, and metal oxides, with different structural dimensionalities (1D, 2D, and 3D) and morphological scales (nano, micro, and bulk). It looks at metal-ion batteries, electrocatalysis, photocatalysis, supercapacitors, photovoltaics, and light-emitting diodes. The field of porous metal/covalent-organic frameworks takes advantage of multi-functionalities and applications in energy. Their compositional designability, structural diversity, and high porosity offer potential in the preparation of materials with different dimensionalities, scales, and morphologies. Prof. Kitagawa and coworkers summarize the synthesis, dimensionality and electrochemical energy storage applications of crystalline porous materials. Prof. Serre et al. summarize the recent advances in the synthesis and potential energy applications of metal–organic frameworks based core–shell composites. Prof. Pang and co-workers detail the energy conversion and storage of metal-organic framework nanocomposites with different dimensionalities (article number 2100346). Prof. Xu and co-workers provide a summary of micro/nano-scaled metal-organic frameworks for energy applications (article number 2003970), and Prof. Zou and co-workers overview the multi-scaled design of metal-organic framework-derived materials and their applications in electrocatalysis (article number 2003410). Compared to 3D bulk metal/covalent-organic frameworks, the large porosity and ultrathin structures of 2D materials contribute to their many striking properties, such as large surface areas and enhanced electrical conductivities. In this regard, Prof. Jang and co-workers summarize the applications of 2D metal/covalent-organic frameworks in the field of electrocatalysis (article number 2003990), Prof. Eddaoudi and co-workers outline 2D covalent-organic framework-based electrodes for supercapacitors and metal-ion batteries (article number 2100177), and Prof. Bu and co-workers summarize the metal/covalent-organic framework based cathodes for metal-ion batteries (article number 2100172). In addition, Profs. Fischer, Cao, and their co-workers discuss the thin film applications of metal/covalent-organic frameworks in the field of electrochemical catalysis (article number 2003499). Furthermore, a number of metal/covalent-organic frameworks exhibit dynamic behaviors under external stimuli, specifically the single-crystal-to-single-crystal phase transition materials were summarized by Profs. Bu and Xu and co-workers (article number 2100324), and the dynamically controlled electronic behavior of stimuli-responsive materials was well-documented by Prof. Shustova and her coworkers (article number 2100441). Metal halide perovskites attract attention in view of their superior photovoltaic and optoelectronic applications. Prof. Zhang and co-workers give a detailed summary of the development of monolithic perovskite tandem solar cells (article number 2003628). In this field, formamidinium lead triiodide (FAPbI3) perovskite is a promising material for fabricating highly efficient solar cells. Accordingly, Prof. Yuan and co-workers detail the recent progress in FAPbI3-based perovskite photovoltaics (article number 2100690). The dimensionality of perovskites has been recognized as a critical factor for their photovoltaic and photoelectric properties. Prof. MacManus-Driscoll, Dr. Hoye, and co-workers introduce the role of dimensionality on the optoelectronic properties of both oxide and halide perovskites, bridging the gap between these two less connected areas (article number 2100499). Prof. Wang and co-workers present dimensionality effects on halide perovskite materials and outline their photo(electro)chemical applications (article number 2004002). In addition, the recent progress of quantum-dot-in-perovskite solids with mixed dimensionalities has been overviewed by Prof. Sargent and his co-workers (article number 2100774). Metal oxide materials have been widely applied to energy conversion and storage. Metal ion batteries are considered as the most promising choice for future energy storage which requires both high energy density and reliable safety. The field needs to be further researched on interfacial issues, including high interfacial resistance, inferior electro/chemical compatibility, and dendrite growth. Prof. Zhang and co-workers look at failure mechanisms in solid-state lithium metal batteries (article number 2100748). Prof. Jiao and co-workers summarize the dendrite-free sodium metal batteries based on a 3D confinement strategy (article number 2100359). The electrode material is one of the key components of metal ion batteries. Prof. Cheng and co-workers outline the multi-dimensional nonstoichiometric electrode materials (article number 2100640). Prof. Wang and co-workers detail 2D material-based electrode materials. Li-rich Mn-based layered oxides are outstanding candidates as cathode materials, but the decline of capacity and discharge potential, induced by the phase transformation during the charge-discharge cycling, is a challenge for their practical applications (article number 2100864). Prof. Li and co-workers lend insight into Li-rich Mn-based cathode materials from dimension to lattice, and to atom (article number 2003885). Li-rich and Li-excess oxides are considered as another type of promising cathode materials, however, the irreversible lattice oxygen loss and structural distortion deteriorate the battery reliability. An ion exchange strategy, which could address these issues, has been reviewed by Prof. Zhou and co-workers (article number 2003972). 2D inorganic materials, such as graphene and carbon nitrides, play a very important role in the field of energy and continuous attention is focused on this direction. Prof. Zhou and co-workers review the recent advances in 2D electro- and photocatalysts, from a combined viewpoint of experiments and computation (article number 2003841). A carbon and carbon-nitride family of materials have been widely applied to energy conversion and storage. Prof. Yang and co-workers give a detailed summary of carbon-based materials in energy storage devices in terms of dimensionality, function, and performance (article number 2100775). Prof. Lotsch and co-workers summarize the structure- and dimensionality-dependent properties of carbon-nitride materials for photo(electro)-chemical energy conversion and storage (article number 2101078). The guest editors seek to provide, via this AENM special issue, a broad perspective on emerging energy materials, and to promote interdisciplinary collaborations among materials scientists, chemists, physicists, and engineers worldwide. We are sincerely grateful to all the authors and reviewers, and the editorial team of AENM (Dr. Muxian Shen, Dr. Bo Weng et al.) for their generous support and dedication to this special issue. The authors declare no conflict of interest.