Developing new materials for the fabrication of proton exchange membranes (PEMs) for fuel cells is of great significance. Herein, a series of highly crystalline, porous, and stable new covalent ...organic frameworks (COFs) have been developed by a stepwise synthesis strategy. The synthesized COFs exhibit high hydrophilicity and excellent stability in strong acid or base (e.g., 12 m NaOH or HCl) and boiling water. These features make them ideal platforms for proton conduction applications. Upon loading with H3PO4, the COFs (H3PO4@COFs) realize an ultrahigh proton conductivity of 1.13×10−1 S cm−1, the highest among all COF materials, and maintain high proton conductivity across a wide relative humidity (40–100 %) and temperature range (20–80 °C). Furthermore, membrane electrode assemblies were fabricated using H3PO4@COFs as the solid electrolyte membrane for proton exchange resulting in a maximum power density of 81 mW cm−2 and a maximum current density of 456 mA cm−2, which exceeds all previously reported COF materials.
Conducting COFs: A stepwise synthesis strategy for the preparation of a series of highly robust COFs with ultrahigh proton conduction was developed. These COFs achieved a record‐high proton conductivity (1.13×10−1 S cm−1) after doping with H3PO4 and were used as the proton exchange membrane of a membrane electrode assembly, which achieved a maximum power output of 81 mW cm−1.
The development of new techniques and materials that can separate ethylene from ethane is highly relevant in modern applications. Although adsorption-based separation techniques using metal–organic ...frameworks (MOFs) have gained increasing attention, the relatively low stability (especially water resistance) and unscalable synthesis of MOFs severely limit their application in real industrial scenarios. Addressing these challenges, we rationally designed and synthesized two new C2H6-selective MOF adsorbents (NKMOF-8-Br and -Me) with ultrahigh chemical and thermal stability, including water resistance. Attributed to the nonpolar/hydrophobic pore environments and appropriate pore apertures, the MOFs can capture C2 hydrocarbon gases at ambient conditions even in high humidity. The single-crystal structures of gas@NKMOF-8 realized the direct visualization of adsorption sites of the gases. Both the single-crystal data and simulated data elucidate the mechanism of selective adsorption. Moreover, the NKMOF-8 possesses high C2H6 adsorption capacity and high selectivity, allowing for efficient C2H6/C2H4 separation, as verified by experimental breakthrough tests. Most importantly, NKMOF-8-Br and -Me can be scalably synthesized through stirring at room temperature in minutes, which confers them with great potential for industrial application. This work offers new adsorbents that can address major chemical industrial challenges and provides an in-depth understanding of the gas binding sites in a visual manner.
Enzyme immobilization has been demonstrated to be a favorable protocol to promote industrialization of biomacromolecules. Despite tremendous efforts to develop new strategies and materials to realize ...this process, maintaining enzyme activity is still a formidable challenge. Herein we created a sacrificial templating method, using metal–organic frameworks (MOFs) as sacrificial templates to construct hollow covalent organic framework (COF) capsules for enzyme encapsulation. This strategy can provide a capacious microenvironment to unleash enzyme molecules. The improved conformational freedom of enzymes, enhanced mass transfer, and protective effect against the external environment ultimately boosted the enzymatic activities. We also found that this strategy possesses high versatility that is suitable for diverse biomacromolecules, MOF templates, and COF capsules. Moreover, the dimensions, pore sizes, and shell thickness of COF capsules can be conveniently tuned, allowing for customizing bioreactors for specific functions. For example, coencapsulation of different enzymes with synergistic functions were successfully demonstrated using this bioreactor platform. This study not only opens up a new avenue to overcome the present limitations of enzymatic immobilization in porous matrixes but also provides new opportunities for construction of biomicrodevices or artificial organelles based on crystalline porous materials.
A molecular porous material, MPM‐2, comprised of cationic Ni2(AlF6)(pzH)8(H2O)2 and anionic Ni2Al2F11(pzH)8(H2O)2 complexes that generate a charge‐assisted hydrogen‐bonded network with pcu topology ...is reported. The packing in MPM‐2 is sustained by multiple interionic hydrogen bonding interactions that afford ultramicroporous channels between dense layers of anionic units. MPM‐2 is found to exhibit excellent stability in water (>1 year). Unlike most hydrogen‐bonded organic frameworks which typically show poor stability in organic solvents, MPM‐2 exhibited excellent stability with respect to various organic solvents for at least two days. MPM‐2 is found to be permanently porous with gas sorption isotherms at 298 K revealing a strong affinity for C2H2 over CO2 thanks to a high (ΔQst)AC Qst (C2H2) − Qst (CO2) of 13.7 kJ mol−1 at low coverage. Dynamic column breakthrough experiments on MPM‐2 demonstrated the separation of C2H2 from a 1:1 C2H2/CO2 mixture at 298 K with effluent CO2 purity of 99.995% and C2H2 purity of >95% after temperature‐programmed desorption. C‐H···F interactions between C2H2 molecules and F atoms of AlF63− are found to enable high selectivity toward C2H2, as determined by density functional theory simulations.
MPM‐2 is the first Molecular Porous Material comprised of coordinated AlF63− and Al2F115− units. It has a strong sorption preference to C2H2 and exhibits dynamic breakthrough column separation of C2H2 from a 1:1 mixture of C2H2/CO2. Efficient C2H2 separation is enabled by a binding site offering strong electrostatic interactions between C2H2 and F‐atoms of AlF63− moieties as indicated by density functional theory (DFT).
A series of increasingly large silver nanoclusters with a varied combination of Archimedean and/or Platonic solid arrangements was constructed using a flexible trifurcate TiL3 (L = Salicylic acid or ...5-fluorosalicylic acid) metalloligand: Ag4@Ag4@Ti4 (PTC-85), Ag12@Ti4 (PTC-86), Ag4@Ag6@Ag12@Ti4 (PTC-87), Ag6@Ag24@Ag12@Ti4 (PTC-88), and Ag12@Ag24@Ti4 (PTC-89). The silver nanoclusters are each capped by four TiL3 moieties, thereby forming {Ti4} supertetrahedra with average edge lengths ranging from ∼8.12 Å to ∼17.37 Å. Such {Ti4} moieties further induce the tetrahedral geometry of the encapsulated silver nanoclusters. These atomically precise metallic clusters were found to be ultrastable with respect to air for several months, and to water for more than 3 days, due to the stabilizing effects of the TiL3 metalloligand. Moreover, the obtained clusters exhibit nonlinear optical (NLO) effects in optical limiting tests and also temperature-dependent photoluminescent properties. This work provides an interesting metalloligand method not only to induce the spatial growth of metallic clusters to achieve highly symmetric structures, but also to enhance their stability which is crucial for future application.
Fabrication of zeolite‐like metal–organic frameworks (ZMOFs) for advanced applications, such as enzyme immobilization, is of great interest but is a great synthetic challenge. Herein, we have ...developed a new strategy using proteins as structure‐directed agents to direct the formation of new ZMOFs that can act as versatile platforms for the in situ encapsulation of proteins under ambient conditions. Notably, protein incorporation directs the formation of a ZMOF with a sodalite (sod) topology instead of a non‐porous diamondoid (dia) topology under analogous synthetic conditions. Histidines in proteins play a crucial role in the observed templating effect. Modulating histidine content thereby influenced the resultant MOF product (from dia to dia + sod mixture and, ultimately, to sod MOF). Moreover, the resulting ZMOF‐incorporated proteins preserved their activity even after exposure to high temperatures and organic solvents, demonstrating their potential for biocatalysis and biopharmaceutical applications.
Caught in a trap: Proteins are used to direct the formation of new zeolitic metal–organic frameworks (MOFs) that encapsulate the template proteins under ambient conditions. Histidines in the proteins play a crucial role in directing the formation of these MOFs. The MOF‐encapsulated proteins retain their activity even after exposure to high temperature and organic solvents.
Many ancient cities around the world were known with their livability. However, these cities started to lose this feature, when vehicles became prior to pedestrians who lost their sense of place, as ...many negative impacts came along. In return, people escaped the city’s core searching for lively districts with attractive streets where the human basic activities can be performed. As a result, dead city centers were left behind. The present paper work proposes an integrative literature between the pedestrianization and livability, then analyze the precedent approaches to pedestrianization in global review, and introduce a creative implementation approach to pedestrianization in order to achieve the following objectives: (1) a tool to break the various barriers that may face implementation, (2) a method of exploration regarding the potential of the misused asphalt, (3) a tactic to re-attract people to the city’s core and its walkable environment and finally, (4) restore the city’s livability thus its sustainable urban development. From this perspective, by rejuvenating the core of a city, the entire city’s livability could be restored, causing a sustainable urban development, through the creative tactical urbanism. Also, the paper includes an analysis of international examples, based on the criterion of tactical urbanism practices.
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