Covalent organic frameworks (COFs) have attracted growing interest by virtue of their structural diversity and tunability. Herein, we present a novel approach for the development of organic rechargeable battery cathodes in which three distinct redox-active COFs were successfully prepared and delaminated into 2D few-layer nanosheets. Compared with the pristine COFs, the exfoliated COFs with shorter Li diffusion pathways allow a significant higher utilization efficiency of redox sites and faster kinetics for lithium storage. Unlike diffusion-controlled manners in the bulk COFs, the redox reactions in ECOFs are mainly dominated by charge transfer process. The capacity and potential are further engineered by reticular design of COFs without altering the underlying topology. Specifically, DAAQ-ECOF exhibits excellent rechargeability (98% capacity retention after 1800 cycles) and fast charge-discharge ability (74% retention at 500 mA g as compared to at 20 mA g). DABQ-ECOF shows a specific capacity of 210 mA h g and a voltage plateau of 2.8 V.

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To the Editors-Electrochemical conversion of dinitrogen to ammonia in aqueous electrolyte solutions at high selectivity and rate requires a catalyst with unique properties. In particular, the surface of such a catalyst should exhibit higher affinity for nitrogen, as opposed to hydrogen, to facilitate the nitrogen reduction reaction (NRR) and suppress the hydrogen evolution reaction (HER). Detailed density functional theory (DFT) studies by Skúlason and co-workers 3 suggest that this is hardly possible with most metals traditionally considered in electrocatalytic research. One metal not included in the analysis in ref. 3 and long known to be a very poor HER catalyst 4 is bismuth, which was very recently introduced by Hao et al. 1 as an efficient NRR catalyst in their report in Nature Catalysis. However, DFT data reported in the same paper clearly indicate that N2 adsorption on various bismuth surfaces is highly thermodynamically unfavourable with an essentially insurmountable energy barrier of more than 2.7 eV. Nevertheless, despite this contradiction, the highly impressive experimental data on the Bicatalysed NRR reported by Hao et al. 1 present the best performances reported to date and therefore would represent important progress in this field. This prompted us to attempt to reproduce these experimental results. Details of our materials and equipment are provided

Air filtration has become an essential need for passive pollution control. However, most of the commercial air purifiers rely on dense fibrous filters, which have good particulate matter (PM) removal capability but poor biocidal effect. Here we present the photocatalytic bactericidal properties of a series of metal-organic frameworks (MOFs) and their potentials in air pollution control and personal protection. Specifically, a zinc-imidazolate MOF (ZIF-8) exhibits almost complete inactivation of Escherichia coli ( E. coli ) (>99.9999% inactivation efficiency) in saline within 2 h of simulated solar irradiation. Mechanistic studies indicate that photoelectrons trapped at Zn + centers within ZIF-8 via ligand to metal charge transfer (LMCT) are responsible for oxygen-reduction related reactive oxygen species (ROS) production, which is the dominant disinfection mechanism. Air filters fabricated from ZIF-8 show remarkable performance for integrated pollution control, with >99.99% photocatalytic killing efficiency against airborne bacteria in 30 min and 97% PM removal. This work may shed light on designing new porous solids with photocatalytic antibiotic capability for public health protection.

Environmental challenges especially air pollution (particulate matter (PM) and toxic gases) pose serious threats to public health globally. Metal-organic frameworks (MOFs) are crystalline materials with high porosity, tunable pore size, and rich functionalities, holding the promise for poisonous pollutants capture. Here, nanocrystals of four unique MOF structures are processed into nanofibrous filters (noted as MOFilter) with high MOF loadings (up to 60 wt %). The MOFilters show high PM removal efficiencies up to 88.33 ± 1.52% and 89.67 ± 1.33% for PM2.5 and PM10, respectively, in the hazy environment, and the performance remains largely unchanged over 48 h of continuous filtration. For the first time, the interactions between such porous crystalline material and particulate pollutants were explored. These thin MOFilters can further selectively capture and retain SO2 when exposed to a stream of SO2/N2 mixture, and their hierarchical nanostructures can easily permeate fresh air at high gas flow rate with the pressure drop <20 Pa.

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ZIF-67, a MOF with N-coordinated Co atoms, can assist the formation of active sites in oxygen reduction catalysts by pyrolysis and acid leaching.

Three-dimensional covalent organic frameworks (3D COFs) are promising crystalline materials with well-defined structures, high porosity, and low density; however, the limited choice of building blocks and synthetic difficulties have hampered their development. Herein, we used a flexible and aliphatic macrocycle, namely γ-cyclodextrin (γ-CD), as the soft struts for the construction of a polymeric and periodic 3D extended network, with the units joined via tetrakis(spiroborate) tetrahedra with various counterions. The inclusion of pliable moieties in the robust open framework endows these CD-COFs with dynamic features, leading to a prominent Li ion conductivity of up to 2.7 mS cm at 30 °C and excellent long-term Li ion stripping/plating stability. Exchanging the counterions within the pores can effectively modulate the interactions between the CD-COF and CO molecules.