New Talent 2022

The 2022 New Talent themed issue is a collection of significant contributions from young researchers to the field of crystal engineering. The breadth of science covered in the 13 articles highlights the extent to which crystal engineering concepts are pervasive in chemistry and applications such as solar cell research, biomedicine, battery technology and hydrogen production. For example, efficient electrocatalysts are critical to producing green hydrogen at economically competitive prices. An area of current interest is to develop catalysts that do not utilize rare, precious metals such as Ru, Pt, and Ir. Yoon Suk Lee and co-workers aim to address this challenge by fabricating La-doped cobalt phosphide (https://doi.org/10.1039/D2CE00599A). Their strategy focused on depositing ZIF-67, a ZIF material composed of 2-methylimidazolate and Co²⁺ ions, on carbon cloth followed by conversion of the ZIF to La–Co(OH)₂via solvothermal treatment in the presence of La(NO₃)₂. A subsequent phosphorization process yielded La–CoP. The authors used La–CoP as both the cathode and anode for the overall water splitting which outperformed a cell composed of Pt/C and RuO₂. Importantly, they showed that La doping afforded greater access to catalytic sites by giving rise to distortions in the CoP lattice. The fundamental knowledge garnered from this study may help the design of novel electrocatalysts for hydrogen generation.

Zeolitic imidazolate frameworks (ZIFs) are known to spontaneously form protective coatings around biomacromolecules, for example enzymes and DNA, via a process termed biomimetic mineralisation. Studies have shown that for ZIF-8, composed of 2-methylimidazole and Zn²⁺ ions, a variety of structural polymorphs can form that possess distinct properties, such as solvent stability and porosity. In their contribution to the new talent issue, Hafner, Villanova and Carraro (https://doi.org/10.1039/D2CE00073C) present a web application that uses an internal standard to facilitate rapid phase analysis of ZIF-based biocomposites. This simple method for determining ZIF phases will be of significant value to research in drug delivery where the stability and, in turn, the release profile of the ZIF-based composite is directly related to its structure.

The ‘building block’ approach to metal–organic frameworks allows for functional components incorporated into their structure. Hua and co-workers (https://doi.org/10.1039/D2CE00103A) show that by employing metalloporphyrins as the organic ‘linker’ Cd-based MOFs can be employed as colorimetric sensors for electron donors. The reported MOFs possess a novel topology for porphyrin frameworks that maximise the percentage of guest binding sites on the porphyrin moieties within the framework. Given the large pore channels of 18.5 Å it is anticipated that MOFs based on this structure may also find application in catalysis.

It is well established that the 3D structure of proteins is influenced by hydrogen bonding between their constituent amino acids. In comparison to hydrogen bonding, our understanding of halogen bonding in biology is in its infancy. Pizzi, Metrangolo, and co-workers contribute to our knowledge of halogen interactions in biology with their report on bonding interactions between bis-halogenated tyrosine molecules (https://doi.org/10.1039/D2CE00670G). They show, via single crystal X-ray diffraction (SCXRD) studies, that dibromo and dichloro tyrosine moieties form structurally distinct crystals. The energies of the interactions identified via SCXRD were also estimated using DFT calculations. This work is an excellent example of how halogen bonding may affect supramolecular interactions in biological systems.

Studying the structural chemistry of new materials is of intrinsic scientific value. Metal thiocyanate perovskite-analogues are a burgeoning class of materials that contain isolated paramagnetic cations; however, their magnetic properties have not been investigated. In this work, Cliffe and co-workers employ neutron powder diffraction to better understand the magnetic interactions in the chromium based thiocyanate, Cr[Bi(SCN)₆]·xH₂O (https://doi.org/10.1039/D2CE00649A). They conclude that the unique magnetic properties of Cr[Bi(SCN)₆]·xH₂O coupled with the broad scope for modifying the structure and chemical composition of metal thiocyanates may lead to the design of novel magnetic materials.

The precise conformation of a bioactive molecule is key to its activity. This motivated Sajesh Thomas and co-workers to study the conformational preferences of a series of molecules that possess α-hydroxy ketone moieties, which are building blocks for biologically active heterocycles and α-functionalized ketones (https://doi.org/10.1039/D2CE00700B). The research team carried out a comprehensive analysis that included SCXRD, theoretical calculations, and a survey of structures in the CSD to ascertain inter- and intramolecular forces that give rise to observed conformations in the selected molecules. The results of this study will be of interest to researchers seeking to understand how molecules that contain α-hydroxy ketone units interact with proteins.

Solvent molecules trapped inside the pores of MOFs often compromise the gas sorption properties, thus necessitating the development of non-solvothermal synthetic methods. Milner and co-workers prepared Mg₂(m-dobdc) by using a mechanochemical method and found its superior gas sorption ability to that of solvothermally prepared Mg₂(m-dobdc) (https://doi.org/10.1039/d2ce00739h). Their work clearly demonstrates the great potential of mechanochemical synthetic routes to MOFs in procuring the great gas storage ability of them. Further extension of their synthetic endeavor to other MOFs is thus highly anticipated.

Metal oxides have been extensively employed to fabricate charge transporting layers in perovskite solar cells due to their desirable properties such as high transparency, stability, and low-cost synthetic routes. Lee and Mahapatra systematically described the innate properties and roles of metal oxides in perovskite solar cells, by placing special emphasis on the doping-induced property tuning of oxides and surface passivation strategies (https://doi.org/10.1039/d2ce00825d). They also provided current limits and challenges of metal oxide-based charge transporting layers and went on further to suggest exploitive venues for future research. It is obvious that their work, serving as a springboard for disruptive research outburst, will attract great attention from the perovskite solar cell research community.

Stimuli-responsive materials have never failed to attract great attention from the materials science community due to the limitless application potentials in many technological fronts. However, the stimuli responsiveness as a function of crystallinity is an area largely unexplored. Nath and co-workers discovered that polycrystalline hydrazone-based aggregates show photoresponsive bending while the single-crystalline counterparts do not show response to light at all (https://doi.org/10.1039/d2ce00829g). This work nicely demonstrates that the crystalline nature of micro- and nano-objects must be considered as a critical factor determining the photo-responsiveness of them.

Co-crystallized organic compounds often show different optical properties from that of the single-component crystal, and it is very difficult to identify the origin of newly derived optical properties. Vasylyeva and co-workers studied the co-crystallization behavior of roseolumiflavin and discovered that the presence of a second component in the co-crystal affects the crystal packing motif most (https://doi.org/10.1039/d2ce00589a). Compared to intermolecular interaction between roseolumiflavin and the crystallization partner, the degree of flavin–flavin interaction is more important in determining the optical properties of roseolumiflavin. This work clearly points to the fact that interaction between key optical components is governed by different crystal structures induced by the second component. Therefore, the fine interactions of optical organic compounds should be carefully assessed in deciphering the optical properties of co-crystals.

Porous materials such as MOFs hold great promise in important application fields such as gas storage and catalysis. However, porous materials can experience structural deformation during operations, which poses a serious problem in accurately understanding the change in the pore size distribution. This matter is aggravated when the porous crystalline materials feature hierarchical architectures. Evans demonstrated an elegant statistical method that provides an accurate measure of pore size distributions for samples with a few different pore sizes (https://doi.org/10.1039/d2ce00696k). With an appropriate exposure of the method to the scientific community, Evans' method would become a cornerstone for advances in the application of various crystalline and hierarchical porous materials.

Perovskites are at the forefront of many technological fields and continue to attract considerable interest. The discovery of perovskites with new compositions is greatly welcomed because the new compositions would naturally imply further application venues. Yeung and co-workers worked on the development of hybrid organic–inorganic perovskites based on the A-site MDABCO dication (MDABCO = N-methyl-N′-diazabicyclo[2.2.2]octonium) and successfully demonstrated the synthesis of [MDABCO]CsI₃, [MDABCO]RbBr₃ and [MDABCO]NH₄Cl₃ (https://doi.org/10.1039/d2ce00848c). They went on further to explain why these compositions, not others, could be obtained by using the two criteria of the Goldschmidt tolerance factor and octahedral factor. The perovskites compositions at the boundaries of the Goldschmidt tolerance factor and octahedral factor hold great material application promise, serving as the next synthetic targets.

The growth of dendrites on lithium metal anodes are a cause of, at times catastrophic, battery failure. As a consequence, researchers are actively working on strategies to prevent their occurrence. Lei et al. employ a glass fibre separator modified with polydimethylsiloxane (PDMS) and show that it leads to desolvation of lithium ions and inhibition of dendrite formation (https://doi.org/10.1039/D2CE00595F). This simple approach leads to a ca. 5-fold improvement in the electrochemical performance of a Li/Li symmetric cell. This chemistry provides insight into how dendrite growth may be avoided in the design of Li-ion batteries.

Although this issue is abbreviated, the scientific quality of the works provided by the young scientists is not and clearly points to the bright future of the field of crystal engineering. Finally, we thank all the emerging scientists contributing to this themed issue, reviewers for their time and feedback, and to the CrystEngComm editorial office for their wonderful efforts.

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