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Here we report the synthesis and crystallization of a -COOH-capped N -heterocyclic carbene (NHC)-protected Au 13 cluster. The single-crystal structure of the -COOH-capped NHC-Au 13 cluster reveals a classic icosahedral core with one Au atom in its center. The icosahedral core is surrounded by five NHC ligands with pseudo C5 symmetry and exposed carboxyls in a pentagonal antiprism fashion. The detailed formula of the Au cluster was identified as Au 13 (bi-NHC carboxyl) 5 Cl 2 (hereafter abbreviated as Au 13 -c). The density functional theory (DFT) calculations confirm that Au 13 -c is an electronically stable eight-electron super-atom cluster and elucidate its optical transitions in the UV-Vis range. The Au 13 -c cluster exhibits excellent thermal and chemical stability under bio-relevant conditions. Additionally, this cluster shows a strong red emission in DMF and H 2 O with an excellent quantum yield (QY) of 40% and 12.6%, respectively. The high QY of Au 13 -c enables its use in cell imaging on both cancer and noncancerous cells., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

Reticular materials constructed from regular molecular building blocks (MBBs) have been widely explored in the past three decades. Recently, there has been increasing interest in the assembly of novel, intricate materials using less-symmetric ligands; however, current methods for predicting structure are not amenable to this increased complexity. To address this gap, we propose herein a generalised version of the net-clipping approach for anticipating the topology of metal-organic frameworks (MOFs) assembled from organic linkers and different polygonal and polyhedral MBBs. It relies on the generation of less-symmetric nets with less-connected linkers, via the rational deconstruction of more-symmetric and more-connected linkers in edge-transitive nets. We applied our top-down strategy to edge-transitive nets containing 4-c tetrahedral, 6-c hexagonal, 8-c cubic or 12-c hexagonal prism linkers, envisaging the formation of 102 derived and 46 clipped nets. Among these, we report 33 new derived nets ( icn 7- icn 39) and 6 new clipped nets ( icn 1- icn 6). Importantly, the feasibility of using net-clipping to anticipate clipped nets is supported by literature examples and new experimental additions. Finally, we suggest and illustrate that net-clipping can be extended to less-regular, non-edge transitive nets as well as to covalent-organic frameworks (COFs), thus opening new avenues for the rational design of new reticular materials exhibiting unprecedented topologies., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Direct air capture is regarded as a plausible alternate approach that, if economically practical, can mitigate the increasing carbon dioxide emissions associated with two of the main carbon polluting sources, namely stationary power plants and transportation. Here we show that metal-organic framework crystal chemistry permits the construction of an isostructural metal-organic framework (SIFSIX-3-Cu) based on pyrazine/copper(II) two-dimensional periodic 4(4) square grids pillared by silicon hexafluoride anions and thus allows further contraction of the pore system to 3.5 versus 3.84 Å for the parent zinc(II) derivative. This enhances the adsorption energetics and subsequently displays carbon dioxide uptake and selectivity at very low partial pressures relevant to air capture and trace carbon dioxide removal. The resultant SIFSIX-3-Cu exhibits uniformly distributed adsorption energetics and offers enhanced carbon dioxide physical adsorption properties, uptake and selectivity in highly diluted gas streams, a performance, to the best of our knowledge, unachievable with other classes of porous materials.