Modular Design of Highly Stable Semiconducting Porous Coordination Polymer for Efficient Electrosynthesis of Ammonia.

Developing highly stable porous coordination polymers (PCPs) with integrated electrical conductivity is crucial for advancing our understanding of electrocatalytic mechanisms and the structure-activity relationship of electrocatalysts. However, achieving this goal remains a formidable challenge because of the electrochemical instability observed in most PCPs. Herein, we develop a "modular design" strategy to construct electrochemically stable semiconducting PCP, namely, Fe-pyNDI, which incorporates a chain-type Fe-pyrazole metal cluster and π-stacking column with effective synergistic effects. The three-dimensional electron diffraction (3D ED) technique resolves the precise structure. Both theoretical and experimental investigation confirms that the π-stacking column in Fe-pyNDI can provide an efficient electron transport path and enhance the structural stability of the material. As a result, Fe-pyNDI can serve as an efficient model electrocatalyst for nitrate reduction reaction (NO3RR) to ammonia with a superior ammonia yield of 339.2 µmol h-1 cm-2 (14677 µg h-1 mgcat. -1) and a faradaic efficiency of 87 % at neutral electrolyte, which is comparable to state-of-the-art electrocatalysts. The in-situ X-ray absorption spectroscopy (XAS) reveals that during the reaction, the structure of Fe-pyNDI can be kept, while part of the Fe3+ in Fe-pyNDI was reduced in situ to Fe2+, which serves as the potential active species for NO3RR.

Diffusion-rate sieving of propylene and propane mixtures in a cooperatively dynamic porous crystal.

Selective molecular recognition is an important alternative to the energy-intensive industrial separation process. Porous coordination polymers (PCPs) offer designing platforms for gas separation because they possess precise controllability over structures at the molecular level. However, PCPs-based gas separations are dominantly achieved using strong adsorptive sites for thermodynamic recognition or pore-aperture control for size sieving, which suffer from insufficient selectivity or sluggish kinetics. Developing PCPs that work at high temperatures and feature both high uptake capacity and selectivity is urgently required but remains challenging. Herein, we report diffusion-rate sieving of propylene/propane (C3H6/C3H8) at 300 K by constructing a PCP material whose global and local dynamics cooperatively govern the adsorption process via the mechanisms of the gate opening for C3H6 and the diffusion regulation for C3H8, respectively, yielding substantial differences in both uptake capacity and adsorption kinetics. Dynamic separation of an equimolar C3H6/C3H8 mixture reveals outstanding sieving performance with a C3H6 purity of 99.7% and a separation factor of 318.

Nonradical Surface Chemistry Mechanisms for Catalytic Nanoparticles.

All radical-detecting methods using trapping agents, which are originally developed for homogeneous reaction systems, may not be applicable to systems with solid surfaces. This is because false radical signals can be generated in the presence of solid surfaces. An extra selectivity study following the trapping agent experiment may help in distinguishing between the true and false radical signals. Surface chemistry mechanisms are superior to free-radical mechanisms in not only correctly understanding the reaction selectivity previously reported for catalytic nanoparticles but also developing theoretical models for the computational design of solid catalysts in the future.

Switching molecular recognition selectivities by temperature in a diffusion-regulatory porous material.

Over the long history of evolution, nature has developed a variety of biological systems with switchable recognition functions, such as the ion transmissibility of biological membranes, which can switch their ion selectivities in response to diverse stimuli. However, developing a method in an artificial host-guest system for switchable recognition of specific guests upon the change of external stimuli is a fundamental challenge in chemistry because the order in the host-guest affinity of a given system hardly varies along with environmental conditions. Herein, we report temperature-responsive recognition of two similar gaseous guests, CO2 and C2H2, with selectivities switched by temperature change by a diffusion-regulatory mechanism, which is realized by a dynamic porous crystal featuring ultrasmall pore apertures with flip-flop locally-motive organic moiety. The dynamic local motion regulates the diffusion process of CO2 and C2H2 and amplifies their rate differences, allowing the crystal to selectively adsorb CO2 at low temperatures and C2H2 at high temperatures with separation factors of 498 (CO2/C2H2) and 181 (C2H2/CO2), respectively.

A natural biogenic nanozyme for scavenging superoxide radicals.

Biominerals, the inorganic minerals of organisms, are known mainly for their physical property-related functions in modern living organisms. Our recent discovery of the enzyme-like activities of nanomaterials, coined as nanozyme, inspires the hypothesis that nano-biominerals might function as enzyme-like catalyzers in cells. Here we report that the iron cores of biogenic ferritins act as natural nanozymes to scavenge superoxide radicals. Through analyzing eighteen representative ferritins from three living kingdoms, we find that the iron core of prokaryote ferritin possesses higher superoxide-diminishing activity than that of eukaryotes. Further investigation reveals that the differences in catalytic capability result from the iron/phosphate ratio changes in the iron core, which is mainly determined by the structures of ferritins. The phosphate in the iron core switches the iron core from single crystalline to amorphous iron phosphate-like structure, resulting in decreased affinity to the hydrogen proton of the ferrihydrite-like core that facilitates its reaction with superoxide in a manner different from that of ferric ions. Furthermore, overexpression of ferritins with high superoxide-diminishing activities in E. coli increases the resistance to superoxide, whereas bacterioferritin knockout or human ferritin knock-in diminishes free radical tolerance, highlighting the physiological antioxidant role of this type of nanozymes.

Integrated Computational and Experimental Framework for Inverse Screening of Candidate Antibacterial Nanomedicine.

Nanomedicine is promising for disease prevention and treatment, but there are still many challenges that hinder its rapid development. A major challenge is to efficiently seek candidates with the desired therapeutic functions from tremendously available materials. Here, we report an integrated computational and experimental framework to seek alloy nanoparticles from the Materials Project library for antibacterial applications, aiming to learn the inverse screening concept from traditional medicine for nanomedicine. Because strong peroxidase-like catalytic activity and weak toxicity to normal cells are the desired material properties for antibacterial usage, computational screening implementing theoretical prediction models of catalytic activity and cytotoxicity is first conducted to select the candidates. Then, experimental screening based on scanning probe block copolymer lithography is used to verify and refine the computational screening results. Finally, the best candidate AuCu3 is synthesized in solution and its antibacterial performance over other nanoparticles against S. aureus and E. coli. is experimentally confirmed. The results show the power of inverse screening in accelerating the research and development of antibacterial nanomedicine, which may inspire similar strategies for other nanomedicines in the future.

Carbon dioxide adsorption to UiO-66: theoretical analysis of binding energy and NMR properties.

UiO-66 is one of the most valuable metal-organic frameworks because of its excellent adsorption capability for gas molecules and its high stability towards water. Herein we investigated adsorption of carbon dioxide (CO2), acetone, and methanol to infinite UiO-66 using DFT calculations on an infinite system under periodic-boundary conditions and post-Hartree-Fock (SCS-MP2 and MP2.5) calculations on cluster models. Three to four molecules are adsorbed at each of four µ-OH groups bridging three Zr atoms in one unit cell (named Site I). Six molecules are adsorbed around three pillar ligands, where the molecule is loosely surrounded by three terephthalate ligands (named Site II). Also, six molecules are adsorbed around the pillar ligand in a different manner from that at Site II, where the molecule is surrounded by three terephthalate ligands (named Site III). Totally fifteen to sixteen CO2 molecules are adsorbed into one unit cell of UiO-66. The binding energy (BE) decreases in the order Site I > Site III > Site II for all three molecules studied here and in the order acetone > methanol ≫ CO2 in the three adsorption sites. At the site I, the protonic H atom of the µ-OH group interacts strongly with the negatively charged O atom of CO2, acetone and methanol, which is the origin of the largest BE value at this site. Although the DFT calculations present these decreasing orders of BE values correctly, the correction by post-Hartree-Fock calculations is not negligibly small and must be added for obtaining better BE values. We explored NMR spectra of UiO-66 with adsorbed CO2 molecules and found that the isotropic shielding constants of the 1H atom significantly differ among no CO2, one CO2 (at Sites I, II, or III), and fifteen CO2 adsorption cases (Sites I to III) but the isotropic 17O and 13C shielding constants change moderately by adsorption of fifteen CO2 molecules. Thus, 1H NMR measurement is a useful experiment for investigating CO2 adsorption.

Intrinsic Strain-Mediated Ultrathin Ceria Nanoantioxidant.

Metal oxide nanozymes have emerged as the most efficient and promising candidates to mimic antioxidant enzymes for treatment of oxidative stress-mediated pathophysiological disorders, but the current effectiveness is unsatisfactory due to insufficient catalytic performance. Here, we report for the first time an intrinsic strain-mediated ultrathin ceria nanoantioxidant. Surface strain in ceria with variable thicknesses and coordinatively unsaturated Ce sites was investigated by theoretical calculation analysis and then was validated by preparing ∼1.2 nm ultrathin nanoplates with ∼3.0% tensile strain in plane/∼10.0% tensile strain out of plane. Compared with nanocubes, surface strain in ultrathin nanoplates could enhance the covalency of the Ce-O bond, leading to increasing superoxide dismutase (SOD)-mimetic activity by ∼2.6-fold (1533 U/mg, in close proximity to that of natural SOD) and total antioxidant activity by ∼2.5-fold. As a proof of concept, intrinsic strain-mediated ultrathin ceria nanoplates could boost antioxidation for improved ischemic stroke treatment in vivo, significantly better than edaravone, a commonly used clinical drug.

[Effect of Plasmacytoid Dendritic Cell Dose in Grafts on CMV Infection after Allogeneic Hematopoietic Stem Cell Transplantation].

OBJECTIVE: To investigate the correlation between plasmacytoid dendritic cell (pDC) dose in grafts and the occurrence of cytomegalovirus (CMV) infection after allogeneic hematopoietic stem cell transplantation (allo-HSCT). METHODS: The clinical data of 80 children who received allo-HSCT in Children's Hospital of Soochow University from August 20, 2020 to June 11, 2021 were retrospectively analyzed. Proportions of DC subsets and T-cell subsets in grafts were detected by flow cytometry in order to calculate infused cell dose of each cell. Weekly monitoring of CMV-DNA copies in peripheral blood for each child were performed after transplantation. The last follow-up date was December 31, 2021. RESULTS: All the children gained hematopoietic reconstitution. CMV infection was observed in 51 children (63.8%±5.4%) within the first 100 days after transplantation, including 2 cases developing CMV disease. Univariate analysis indicated that infused doses of DC and pDC were significantly associated with CMV infection within 100 days after allo-HSCT (P <0.05). Multivariate analysis indicated that a high dose infusion of pDC was an independent protective factor for CMV infection within 100 days after allo-HSCT (P <0.05). By the end of follow-up, 7 children died of transplantation-related complications, including 2 deaths from CMV disease, 2 deaths from extensive chronic graft-versus-host disease, and 3 deaths from capillary leak syndrome. The overall survival rate was 91.2%. CONCLUSION: The pDC in grafts may be associated with early infection of CMV after allo-HSCT, while a high infused pDC dose may serve as a protective factor for CMV infection after transplantation.

Soft corrugated channel with synergistic exclusive discrimination gating for CO2 recognition in gas mixture.

Developing artificial porous systems with high molecular recognition performance is critical but very challenging to achieve selective uptake of a particular component from a mixture of many similar species, regardless of the size and affinity of these competing species. A porous platform that integrates multiple recognition mechanisms working cooperatively for highly efficient guest identification is desired. Here, we designed a flexible porous coordination polymer (PCP) and realised a corrugated channel system that cooperatively responds to only target gas molecules by taking advantage of its stereochemical shape, location of binding sites, and structural softness. The binding sites and structural deformation act synergistically, exhibiting exclusive discrimination gating (EDG) effect for selective gate-opening adsorption of CO2 over nine similar gas molecules, including N2, CH4, CO, O2, H2, Ar, C2H6, and even higher-affinity gases such as C2H2 and C2H4. Combining in-situ crystallographic experiments with theoretical studies, it is clear that this unparalleled ability to decipher the CO2 molecule is achieved through the coordination of framework dynamics, guest diffusion, and interaction energetics. Furthermore, the gas co-adsorption and breakthrough separation performance render the obtained PCP an efficient adsorbent for CO2 capture from various gas mixtures.

Nano-Impact Electrochemistry Reveals Kinetics Information of Metal-Ion Battery Materials with Multiple Redox Centers.

Prussian blue (PB) has emerged as a promising cathode material in aqueous batteries. It possesses two distinct redox centers, and the potassium ions (K+ ) are unevenly distributed throughout the compound, adding complexity to the interpretation of the K+ insertion/de-insertion kinetic mechanism. Traditional ensemble-averaged measurements are limited in uncovering the precise kinetic information of the PB particles, as the results are influenced by the construction of the porous composite electrode and the redox behavior from different particles. In this study, the electrochemical processes of individual PB particles were investigated using nano-impact electrochemistry. By varying the potentials, different types of transient current signals were obtained that revealed the kinetic mechanism of each oxidation/reduction reaction in combination with theoretical simulation. Additionally, a partially contradictory conclusion between single-particle analysis and the ensemble-averaged measurement was discussed. These findings contribute to a better understanding of the electrochemical processes of cathode materials with multiple redox centers, which facilitates the development of effective strategies to optimize these materials.

Selective sorption of oxygen and nitrous oxide by an electron donor-incorporated flexible coordination network.

Incorporating strong electron donor functionality into flexible coordination networks is intriguing for sorption applications due to a built-in mechanism for electron-withdrawing guests. Here we report a 2D flexible porous coordination network, [Ni2(4,4'-bipyridine)(VTTF)2]n(1) (where H2VTTF = 2,2'-[1,2-bis(4-benzoic acid)-1,2ethanediylidene]bis-1,3-benzodithiole), which exhibits large structural deformation from the as-synthesized or open phase (1α) into the closed phase (1ß) after guest removal, as demonstrated by X-ray and electron diffraction. Interestingly, upon exposure to electron-withdrawing species, 1ß reversibly undergoes guest accommodation transitions; 1α⊃O2 (90 K) and 1α⊃N2O (185 K). Moreover, the 1ß phase showed exclusive O2 sorption over other gases (N2, Ar, and CO) at 120 K. The phase transformations between the 1α and 1ß phases under these gases were carefully investigated by in-situ X-ray diffraction, in-situ spectroscopic studies, and DFT calculations, validating that the unusual sorption was attributed to the combination of flexible frameworks and VTTF (electron-donor) that induces strong interactions with electron-withdrawing species.

Conjugated Nonplanar Copper-Catecholate Conductive Metal-Organic Frameworks via Contorted Hexabenzocoronene Ligands for Electrical Conduction.

Conductive metal-organic frameworks (c-MOFs) with outstanding electrical conductivities and high charge carrier mobilities are promising candidates for electronics and optoelectronics. However, the poor solubility of planar ligands greatly hinders the synthesis and widespread applications of c-MOFs. Nonplanar ligands with excellent solubility in organic solvents are ideal alternatives to construct c-MOFs. Herein, contorted hexabenzocoronene (c-HBC) derivatives with good solubility are adopted to synthesize c-MOFs. Three c-MOFs (c-HBC-6O-Cu, c-HBC-8O-Cu, and c-HBC-12O-Cu) with substantially different geometries and packing modes have been synthesized using three multitopic catechol-based c-HBC ligands with different symmetries and coordination numbers, respectively. With more metal coordination centers and increased charge transport pathways, c-HBC-12O-Cu exhibits the highest intrinsic electrical conductivity of 3.31 S m-1. Time-resolved terahertz spectroscopy reveals high charge carrier mobilities in c-HBC-based c-MOFs, ranging from 38 to 64 cm2 V-1 s-1. This work provides a systematic and modular approach to fine-tune the structure and enrich the c-MOF family with excellent charge transport properties using nonplanar and highly soluble ligands.

Targeted Synthesis of Isomeric Naphthalene-Based 2D Kagome Covalent Organic Frameworks.

Targeted synthesis of kagome (kgm) topologic 2D covalent organic frameworks remains challenging, presumably due to the severe dependence on building units and synthetic conditions. Herein, two isomeric "two-in-one" monomers with different lengths of substituted arms based on naphthalene core (p-Naph and m-Naph) are elaborately designed and utilized for the defined synthesis of isomeric kgm Naph-COFs. The two isomeric frameworks exhibit splendid crystallinity and showcase the same chemical composition and topologic structure with, however, different pore channels. Interestingly, C60 is able to uniformly be encapsulated into the triangle channels of m-Naph-COF via in situ incorporation method, while not the isomeric p-Naph-COF, likely due to the different pore structures of the two isomeric COFs. The resulting stable C60 @m-Naph-COF composite exhibits much higher photoconductivity than the m-Naph-COF owing to charge transfer between the conjugated skeletons and C60 guests.

Clear-Box Machine Learning for Virtual Screening of 2D Nanozymes to Target Tumor Hydrogen Peroxide.

Targeting tumor hydrogen peroxide (H2 O2 ) with catalytic materials has provided a novel chemotherapy strategy against solid tumors. Because numerous materials have been fabricated so far, there is an urgent need for an efficient in silico method, which can automatically screen out appropriate candidates from materials libraries for further therapeutic evaluation. In this work, adsorption-energy-based descriptors and criteria are developed for the catalase-like activities of materials surfaces. The result enables a comprehensive prediction of H2 O2 -targeted catalytic activities of materials by density functional theory (DFT) calculations. To expedite the prediction, machine learning models, which efficiently calculate the adsorption energies for 2D materials without DFT, are further developed. The finally obtained method takes advantage of both interpretability of physics model and high efficiency of machine learning. It provides an efficient approach for in silico screening of 2D materials toward tumor catalytic therapy, and it will greatly promote the development of catalytic nanomaterials for medical applications.

Fine Pore-Structure Engineering by Ligand Conformational Control of Naphthalene Diimide-Based Semiconducting Porous Coordination Polymers for Efficient Chemiresistive Gas Sensing.

Exploring new porous coordination polymers (PCPs) that have tunable structure and conductivity is attractive but remains challenging. Herein, fine pore structure engineering by ligand conformation control of naphthalene diimide (NDI)-based semiconducting PCPs with π stacking-dependent conductivity tunability is achieved. The π stacking distances and ligand conformation in these isoreticular PCPs were modulated by employing metal centers with different coordination geometries. As a result, three conjugated PCPs (Co-pyNDI, Ni-pyNDI, and Zn-pyNDI) with varying pore structure and conductivity were obtained. Their crystal structures were determined by three-dimensional electron diffraction. The through-space charge transfer and tunable pore structure in these PCPs result in modulated selectivity and sensitivity in gas sensing. Zn-pyNDI can serve as a room-temperature operable chemiresistive sensor selective to acetone.

Separating water isotopologues using diffusion-regulatory porous materials.

The discovery of a method to separate isotopologues, molecular entities that differ in only isotopic composition1, is fundamentally and technologically essential but remains challenging2,3. Water isotopologues, which are very important in biological processes, industry, medical care, etc. are among the most difficult isotopologue pairs to separate because of their very similar physicochemical properties and chemical exchange equilibrium. Herein, we report efficient separation of water isotopologues at room temperature by constructing two porous coordination polymers (PCPs, or metal-organic frameworks) in which flip-flop molecular motions within the frameworks provide diffusion-regulatory functionality. Guest traffic is regulated by the local motions of dynamic gates on contracted pore apertures, thereby amplifying the slight differences in the diffusion rates of water isotopologues. Significant temperature-responsive adsorption occurs on both PCPs: H2O vapour is preferentially adsorbed into the PCPs, with substantially increased uptake compared to that of D2O vapour, facilitating kinetics-based vapour separation of H2O/HDO/D2O ternary mixtures with high H2O separation factors of around 210 at room temperature.

Tunable acetylene sorption by flexible catenated metal-organic frameworks.

The safe storage of flammable gases, such as acetylene, is essential for current industrial purposes. However, the narrow pressure (P) and temperature range required for the industrial use of pure acetylene (100 < P < 200 kPa at 298 K) and its explosive behaviour at higher pressures make its storage and release challenging. Flexible metal-organic frameworks that exhibit a gated adsorption/desorption behaviour-in which guest uptake and release occur above threshold pressures, usually accompanied by framework deformations-have shown promise as storage adsorbents. Herein, the pressures for gas uptake and release of a series of zinc-based mixed-ligand catenated metal-organic frameworks were controlled by decorating its ligands with two different functional groups and changing their ratio. This affects the deformation energy of the framework, which in turn controls the gated behaviour. The materials offer good performances for acetylene storage with a usable capacity of ~90 v/v (77% of the overall amount) at 298 K and under a practical pressure range (100-150 kPa).

Guided Synthesis of a Mo/Zn Dual Single-Atom Nanozyme with Synergistic Effect and Peroxidase-like Activity.

We present a facile route towards a dual single-atom nanozyme composed of Zn and Mo, which utilizes the non-covalent nano-assembly of polyoxometalates, supramolecular coordination complexes as the metal-atom precursor, and a macroscopic amphiphilic aerogel as the supporting substrate. The dual single-atoms of Zn and Mo have a high content (1.5 and 7.3 wt%, respectively) and exhibit a synergistic effect and a peroxidase-like activity. The Zn/Mo site was identified as the main active center by X-ray absorption fine structure spectroscopy and density functional theory calculation. The detection of versatile analytes, including intracellular H2 O2 , glucose in serum, cholesterol, and ascorbic acid in commercial beverages was achieved. The nanozyme has an outstanding stability and maintained its performance after one year's storage. This study develops a new peroxidase-like nanozyme and provides a robust synthetic strategy for single-atom catalysts by utilizing an aerogel as a facile substrate that is capable of stabilizing various metal atoms.

Accelerated discovery of superoxide-dismutase nanozymes via high-throughput computational screening.

The activity of nanomaterials (NMs) in catalytically scavenging superoxide anions mimics that of superoxide dismutase (SOD). Although dozens of NMs have been demonstrated to possess such activity, the underlying principles are unclear, hindering the discovery of NMs as the novel SOD mimics. In this work, we use density functional theory calculations to study the thermodynamics and kinetics of the catalytic processes, and we develop two principles, namely, an energy level principle and an adsorption energy principle, for the activity. The first principle quantitatively describes the role of the intermediate frontier molecular orbital in transferring electrons for catalysis. The second one quantitatively describes the competition between the desired catalytic reaction and undesired side reactions. The ability of the principles to predict the SOD-like activities of metal-organic frameworks were verified by experiments. Both principles can be easily implemented in computer programs to computationally screen NMs with the intrinsic SOD-like activity.