Facile preparation of N-doped corncob-derived carbon nanofiber efficiently encapsulating Fe2O3 nanocrystals towards high ORR electrocatalytic activity

Facile preparation of cost-effective and durable porous carbon-supported non-precious-metal/nitrogen electrocatalysts for oxygen reduction reaction(ORR)is extremely important for promoting the commercialized applications of such catalysts.In this work,the FeCl3-containing porphyrinato iron-based covalent porous polymer(FeCl3·FeP or-CPP)was fabricated in-situ onto porous corncob biomass supports via a simple one-pot method.Subsequent thermal-reduction pyrolysis at 700℃-900℃with CO2 gas as an activating agent resulted in Fe2O3-decorated and N-doped graphitic carbon composite Fe2O3@NC&bio-C with a high degree of graphitization of Fe-involved promotion during pyrolysis(Fe2O3=FeCl3·FePor-CPP derived Fe2O3;NC=N-doped graphene analog;bio-C=the corncob-derived hierarchically porous graphitic biomass carbon framework).The derivedα-Fe2O3 andγ-Fe2O3 nanocrystals(5-10 nm particle diameter)were all immobilized on the N-doped bio-C micro/nanofibers.Notably,the Fe2O3@NC&bio-C obtained at the pyrolysis temperature of 800℃(Fe2O3@NC&bio-C-800),exhibited unusual ORR catalytic efficiency via a 4-electron pathway with the onset and half-wave potentials of 0.96 V and 0.85 V vs.RHE,respectively.In addition,Fe2O3@NC&bio-C-800 also exhibited a high and stable limiting current density of-6.0 mA cm-2,remarkably stability(larger than 91%retention after 10000 s),and good methanol tolerance.The present work represents one of the best results for iron-based biomass material ORR catalysts reported to date.The high ORR activity is attributed to the uniformly distributedα-Fe2O3 andγ-Fe2O3 nanoparticles on the N-enriched carbon matrix with a large specific surface area of 772.6 m^2 g^-1.This facilitates favor faster electron movement and better adsorption of oxygen molecules on the surface of the catalyst.Nevertheless,comparative studies on the structure and ORR catalytic activity of Fe2O3@NC&bioC-800 with Fe2O3@bio-C-800 and NC&bio-C-800 clearly highlight the synergistic effect of the coexisting Fe2O3 nanocrystals,NC,and bio-C on the ORR performance.

In-situ growth of ZnS/FeS heterojunctions on biomass-derived porous carbon for efficient oxygen reduction reaction

It is an urgent task to develop highly efficient non-noble metal electrocatalysts in the direction of ORR,but still a huge and long-term challenge.Herein,an efficient one-step pyrolysis of Sichuan pepper powder,2,2-bipyridine,FeCl3,Na SCN,and ZnCl2 at 900℃ provides the FeS/ZnS@N,S-C-900 hybrid catalyst.Transmission electron microscopy(TEM)images and Mott-Schottky curves clearly reveal the in-situ constructed abundant FeS/ZnS-based p-n junctions dispersed on the biomass-derived porous carbon surface of FeS/ZnS@N,S-C-900.The as-prepared FeS/ZnS@N,S-C-900 hybrid exhibits superior ORR performance in comparison with Pt/C in 0.1 M KOH with high onset(Eonset)and half-wave potentials(E1/2)of 1.00 and 0.880 V vs.RHE,large limiting current density(JL)of 5.60 mA cm-2,and robust durability and methanol tolerance.Impressively,upon the light irradiation,FeS/ZnS@N,S-C-900 produces a photocurrent as high as ca.0.3μA cm-2,resulting in further improvement over Eonset,E1/2,and JLof FeS/ZnS@N,S-C-900 to1.10 V vs.RHE,0.885 V vs.RHE,and 6.02 mA cm-2.Experiment in combination with theoretical calculations demonstrate the significant effect of FeS/ZnS heterojunction on the enhanced ORR catalytic activity of FeS/ZnS@N,S-C-900.This work is useful for the development of advanced heterojunction-based ORR catalysts for various energy conversion devices.

Universal synthesis of metallophthalocyanine covalent organic frameworks as ultra-sensitive multifaceted electrochemical sensor

The universal synthesis of highly stable covalent organic frameworks(COFs)for ultra-sensitive and multi-component electrochemical detection in different scenarios remains a great challenge.Herein,a series of metallophthalocyanine-based twodimensional(2D)dioxin(DXI)-linked metalophthalocyanine(MPc)-n DXI-COFs(M=Ni,Zn;n=1,2)are afforded in high yield(80%-96%)by a facile trace-quinoline assisted one-pot condensation of tetracarbonitrile precursors.Powder X-ray diffraction and electron microscopy investigations disclose their lamellar texture 2D network with AA stacking mode.Experiments and calculation results elucidate that the 2DXI-linked MPc-2DXI-COFs provide the stronger built-in electronic field and more electrostatic/hydrogen bonding adsorption sites than DXI-linked MPc-DXI-COFs,and the lower electrode reaction Gibbs free energy and stronger adsorption of analytes at Ni Pc than Zn Pc unit,which grants Ni Pc-2DXI-COF excellent sensing properties for various analytes including neurotransmitters,organic pollutants,and heavy metal ions,with high sensitivity and low detection limit of 0.53 to 25.66 nM.Especially in binary and ternary systems and even in real-world conditions,simultaneous multi-component detection could be achieved.

Hydrothermal synthesis of polyimide-linked covalent organic frameworks towards ultrafast and stable cathodic sodium storage

Redox-active organic materials are capturing growing attention as cathode materials for sustainable alkaline metal ion batteries.However,the storage of Na+in most organic materials-based cathodes is plagued by low capacity and unsatisfying rate performance due to their low active site densities and limited exposed active sites.Herein,two polyimide-linked covalent organic frameworks(COFs),namely HATN-PD-COF and HATN-TAB-COF,were fabricated from hydrothermal synthesis with redoxactive triphenylene-2,3,6,7,10,11-hexacarboxylic acid and aromatic amines as starting materials.Powder X-ray diffraction and electron microscopy analysis indicate the high crystalline nature of these COFs with AA stacking configuration and orderly mesoporous tunnel.N_(2) sorption measurement discloses the permanent porosity of these two COFs with a Brunauer-EmmettTeller surface area of 1,065-1,200 m^(2)g^(-1)and a large pore size of 2.0-3.1 nm.Galvanostatic intermittent titration technique and density functional theory calculations reveal the facile Na+ion diffusion along the mesoporous tunnel of these COFs with a small energy barrier of 0.13-0.40 e V.In particular,the as-prepared COFs based-cathodes show ultrafast and stable Na+storage associated with their conjugated electronic structure,highly ordered mesoporous tunnel,robust structure,and redox-active C=N/C=O-rich framework as exemplified by the high reversible capacity of 210 m A h g^(-1)at 200 m A g^(-1),record-high rate performance(195 m A h g^(-1)at a high current density of 10,000 m A g^(-1))among organic electrodes and the capacity retention of nearly 91%at 10,000 m A g^(-1)after 7,000 cycles for HATN-PD-COF.

A tetraaldehyde-derived porous organic cage and covalent organic frameworks:Syntheses,structures,and iodine vapor capture

Dynamic covalent imine reactions between 2,3-dimethoxy-[1,1:4,1-terphenyl]-3,3,5,5-tetracarbaldehyde(DMTT)and cyclohexanediamine,p-phenylenediamine,and benzidine,respectively,generate a porous organic cage(DMPOC)and two covalent organic frameworks(COFs),USTB-29,and USTB-30.DMPOC shows a[3+6]topological cage-like structure according to single crystal X-ray diffraction result.In contrast,both microcrystalline USTB-29 and USTB-30 exhibit two-dimensional monoporous structures in an eclipsed AA stacking style based on powder X-ray diffraction and theoretical simulations.In addition,DMPOC is capable of efficiently absorbing the iodine vapor with an outstanding uptake of 5.10 g/g,much higher than that of USTB-29(3.07 g/g)and USTB-30(3.16 g/g).Cage to COFs transformations have been realized from DMPOC to USTB-29 and USTB-30 via the imine bond exchange with slightly increased iodine vapor uptake.Mechanism investigations uncover that both nitrogen and oxygen atoms of POC and COFs contribute to iodine vapor capture due to the formation of charge transfer matter,and loose interaction introducing adaptive expanding voids of DMPOC is suggested to capture more iodine vapor than that of COFs with strongπ-πinteractions.

The 2^(nd)Asian Conference on Porphyrins,Phthalocyanines and Related Materials

In the past decades,porphyrins,phthalocyanines and related materials have attracted significant attention due to their diverse and brilliant structures[1,2],as well as their unique electronic structures and photophysical properties which could be applicable in a wide range of areas[3–5].

Interfacial engineering of SnO_(2)/Bi_(2)O_(2)CO_(3)heterojunction on heteroatoms-doped carbon for high-performance CO_(2)electroreduction to formate

Electrochemical CO_(2)reduction is a viable,economical,and sustainable method to transform atmospheric CO_(2)into carbon-based fuels and effectively reduce climate change and the energy crisis.Constructing robust catalysts through interface engineering is significant for electrocatalytic CO_(2)reduction(ECR)but remains a grand challenge.Herein,SnO2/Bi_(2)O_(2)CO_(3)heterojunction on N,S-codoped-carbon(SnO_(2)/BOC@NSC)with efficient ECR performance was firstly constructed by a facile synthetic strategy.When the SnO_(2)/BOC@NSC was utilized in ECR,it exhibits a large formic acid(HCOOH)partial current density(JHCOOH)of 86.7 mA·cm^(−2)at−1.2 V versus reversible hydrogen electrode(RHE)and maximum Faradaic efficiency(FE)of HCOOH(90.75%at−1.2 V versus RHE),respectively.Notably,the FEHCOOH of SnO_(2)/BOC@NSC is higher than 90%in the flow cell and the JHCOOH of SnO_(2)/BOC@NSC can achieve 200 mA·cm^(−2)at−0.8 V versus RHE to meet the requirements of industrialization level.The comparative experimental analysis and in-situ X-ray absorption fine structure reveal that the excellent ECR performance can be ascribed to the synergistic effect of SnO_(2)/BOC heterojunction,which enhances the activation of CO_(2)molecules and improves electron transfer.This work provides an efficient SnO_(2)-based heterojunction catalyst for effective formate production and offers a novel approach for the construction of new types of metal oxide heterostructures for other catalytic applications.

Metalphthalocyanine frameworks grown on TiO_(2)nanotubes for synergistically and efficiently electrocatalyzing urea production from CO_(2)and nitrate

Electrocatalytic synthesis of urea from CO_(2)and NO_(3)^(-)under ambient conditions provides an appealing alternative to the traditional energy-intensive urea synthetic protocol.Highly active and selective electrocatalysts for efficient urea production are therefore urgently desired owing to the unsatisfactory performance of the thus far reported catalysts.Herein,a phthalocyaninebased(Pc-based)covalent organic framework(COF),namely Co Pc-COF,fabricated from the nucleophilic substitution reaction of hexadecafluorophthalocyaninato cobalt with octahydroxylphthalocyanine cobalt,in situ grew on the surface of multilayered Ti O_(2)nanotubes(NTs),generating the Co Pc-COF@Ti O_(2)NTs composite.Powder X-ray diffraction analysis in combination with electron microscopy measurements discloses the uniform coating of crystalline Co Pc-COF on the multilayered Ti O_(2)NTs in Co Pc-COF@Ti O_(2)NTs.Remarkably,electrochemical tests reveal the superior electrocatalytic activity of Co Pc-COF@Ti O_(2)NTs towards urea production from CO_(2)and NO3-with a record-high yield of 1,205μg h^(-1)cm^(-2)and an outstanding Faraday efficiency of 49%at-0.6 V versus reversible hydrogen electrode due to the significant synergistic catalysis effect.In situ attenuated total reflection infrared spectroscopic investigation and theoretical calculations unveil the efficient C–N coupling reaction between*CO intermediate derived from CO_(2)on Co Pc moieties and*NH2intermediate formed from NO_(3)^(-)on Ti O_(2)NTs during the urea formation process over Co Pc-COF@Ti O_(2)NTs.This work should be helpful towards designing and fabricating high-performance electrocatalysts for sustainable synthesis of urea through efficient synergistic effect of multiactive centers.

High Sensitive Ambipolar Response towards Oxidizing NO2 and Reducing NH3 Based on Bis（phthalocyaninato） Europium Semiconductors

High sensitive chemical sensors towards NO2 and NH3 based on the self-assembled nanostructures of the heteroleptic and homoleptic bis（phthalocyaninato） europium complexes with octanaphthoxy phthalocyaninato ligands named Eu（Pc）[Pc（ONh）8] （1） and Eu[Pc（ONh）8]2 （2） [Pc = unsubstituted phthalocyaninate; Pc（ONh）8 = 2,3,9,10,16,17,23,24-octanaphthoxy phthalocyaninate] have been developed. The good conductivity, high crystal- linity and large specific surface area for the self-assemblies of 1 render it excellent sensing property for either electron-accepting gas NO2 in 50--250 ppb range or electron-donating gas NH3 in 2.5--12.5 ppm range due to the optimized molecular packing in the uniform-sized nanopartieles depending on the effective intermolecular interaction between double-decker molecules, among the best results of phthalocyanine-based chemical sensors for detection of NO2 and NH3 at room temperature. Interestingly, self-assemblies of I exhibited n-type response to NO2 and p-type response to NH3, which is the first example of ambipolar charge-transporting gas sensors fabricated from single- component organic semiconductors. However, the self-assemblies of 2 with sixteen bulky naphtboxy groups at the periphery of two Pc rings only present an n-type response to strong oxidant gas NO2 in a relatively high concentration of 0.5 - 1.5 ppm, while are insensitive to weak reducing gas NH3 due to the existence of great steric hindrance from bulky naphthoxy groups and more traps and/or defects in self-assemblies.

Porous Pyrene Organic Cage with Unusual Absorption Bathochromic-Shift Enables Visible Light Photocatalysis

We have constructed a novel porous pyrene-based organic cage,PyTC1,through the condensation reaction of cyclohexanediamine with 5,5′-(pyrene-1,6-diyl)diisophthalaldehyde.Single-crystal X-ray diffraction analysis reveals the effective intercage C–H...πinteraction between cyclohexanediimine and pyrene segments.Such a soft intercage C–H...πinteraction,rather than a classic J-aggregate with slippedπ–π-stacking configuration,induced an unusual bathochromic shift of pyrene-based chromophore absorption from an ultraviolet region of PyTC1 in solution to the visible light region of PyTC1 in solid-state.

Covalent organic frameworks with imine proton acceptors for efficient photocatalytic H_(2) production

Covalent organic frameworks (COFs) are promising crystalline materials for the light-driven hydrogen evolution reaction (HER) due to their tunable chemical structures and energy band gaps.However,deeply understanding corresponding mechanism is still challenging due to the multiple components and complicated electron transfer and reduction paths involved in photocatalytic HER.Here,the photocatalytic HER investigation has been reported based on three COFs catalysts,1–3,which are prepared by benzo[1,2-b:3,4-b’:5,6-b’]trithiophene-2,5,8-trialdehyde to react with C3symmetric triamines including tris(4-aminophenyl)amine,1,3,5-tris(4-aminophenyl)benzene,and (1,3,5-tris-(4-aminophenyl)triazine,respectively.As the isostructural hexagonal honeycomb-type COF of 2 and 3 reported previously,the crystal structure of 1 has been carefully correlated through the powder X-ray diffraction study with the help of theoretical simulations.1 shows highly porous framework with Brunauer-Emmett-Teller surface area of1249 m^(2)/g.Moreover,the introduction of ascorbic acid into the photocatalytic system of COFs achieves the hydrogen evolution rate of 3.75,12.16 and 20.2 mmol g^(–1)h^(–1) for 1–3,respectively.The important role of ascorbic acid in photocatalysis of HER is disclosed to protonate the imine linkages of these COFs,leading to the obvious absorbance red-shift and the improved charge separation efficiency together with reduced resistance in contrast to pristine materials according to the spectroscopic and electronic characterizations.These innovations of chemical and physical properties for these COFs are responsible for their excellent photocatalytic performance.These results elucidate that tiny modifications of COFs structures is able to greatly tune their band structures as well as catalytic properties,therefore providing an available approach for optimizing COFs functionalities.

Two-dimensional conjugated N-rich covalent organic frameworks for superior sodium storage

Sodium-ion batteries(SIBs) are considered as a promising next-generation energy storage system. To achieve the large-scale application of SIBs, it is crucial to develop cost-effective anode materials with high Na-ion storage capacity. Herein twodimensional(2D) conjugated covalent organic frameworks(c COFs) with N-rich phthalocyanine(Pc) units fused via benzene moieties(named MPc-2D-c COFs) were explored as the SIBs anode materials. Electrochemical tests reveal their high reversible capacities of 538 and 342 m A h g^(-1) at 50 and 1000 m A g^(-1), respectively, good rate performance, and excellent stability,comparable to the state-of-the-art anode materials of SIBs, indicating their outstanding Na-ion storage performance. Ex situ Xray photoelectron and Fourier transform infrared spectroscopies together with theoretical calculations disclose the N atoms at the pore channels and conjugated pyrrole moieties of MPc-2D-c COFs provide abundant Na-ion storage sites. This, in cooperation with the enhanced electrical conductivity owing to the 2D conjugated structure, contributes to the outstanding Na-ion storage capacity of MPc-2D-c COFs. The present result is surely helpful for developing high-performance and cost-effective COFs as electroactive materials for SIBs.

Topochemical polymerization of hydrogen-bonded organic framework for supporting ultrafine palladium nanoparticles

Topochemical polymerization of molecular crystals into porous materials is of significance due to their promising applications in the field of adsorption and catalysis,yet rarely reported due to the synthesis difficulty.Herein,a hydrogen-bonded organic framework(HOF-45)has been fabricated by the crystallization of a cage-like building block containing three alkynyl groups.It exhibits almost mesoporous structure demonstrated by single crystal X-ray diffraction study.Light-driven topochemical polymerization of HOF-45 with ethanedithiol covalently links alkynyl groups in HOF-45,generating a hydrogen-bond and covalentbond cross-linked material(HOF-45C).In contrast to HOF-45,cross-linked HOF-45C retains the crystalline nature and displays improved solution resistence according to the powder X-ray diffraction data.In particular,HOF-45C is able to support the growth of ultrafine palladium nanoparticles with the average size of ca.1.9 nm for rapidly promoting the degradation of nitrophenol,methyl orange,and congo red with the help of NaBH_(4)as well as Suzuki-Miyaura coupling reaction.This work inputs a new idea on the HOFs application in preparing covalent-linked porous organic materials.

High Fluorescence Porous Organic Cage for Sensing Divalent Palladium Ion and Encapsulating Fine Palladium Nanoparticles

Porous organic cages(POCs)as an innovative type of porous molecular materials enable multifunctional applications.Herein,a fluorescence POC(denoted as 1)has been constructed by means of 5/5'-((2/5-dimethoxy-l/4-phenylene)bis(ethyne-2/1-diyl))diiso-phthalaldehyde condensing with cyclohexanediamine enantiomer with the aid of trifluoroacetic acid.1 exhibits the permanent void and prominent fluorescence with relative quantum yield of 73%confirmed by gas sorption and emission experiments,respectively.Moreover,this organic cage is capable of sensing diavalent Pd2+according to the fluorescence response to the addition of various metal ions.The dispersion of 1 in methanol containing palladium acetate was stirred at 25℃and then 80℃to reduce Pd2+ions into nanoparticles(NPs),leading to the composite(Pd@l)composed of fine Pd NPs with the size of co.1.8 nm.The catalytic nature of Pd@l over NaBH4 promoted the degeneration of nitrobenzene and congo red.This work introduces one new case of POCs with versatile properties and functions,including ion fluorescence recognition,fine Pd NPs stabilizer,and gas adsorption,enriching the family of POC-based materials.

Atomic CoN_(3)S_(1) sites for boosting oxygen reduction reaction via an atomic exchange strategy

It is vitally important to develop high-efficiency low-cost catalysts to boost oxygen reduction reaction(ORR)for renewable energy conversion.Herein,an A-CoN_(3)S_(1)@C electrocatalyst with atomic CoN_(3)S_(1)active sites loaded on N,S-codoped porous carbon was produced by an atomic exchange strategy.The constructed A-CoN_(3)S_(1)@C electrocatalyst exhibits an unexpected half-wave potential(0.901 V vs.reversible hydrogen electrode)with excellent durability for ORR under alkaline conditions(0.1 M KOH),superior to the commercial platinum carbon(20 wt.%Pt/C).The outstanding performance of A-CoN_(3)S_(1)@C in ORR is due to the positive effect of S atoms doping on optimizing the electron structure of the atomic CoN_(3)S_(1)active sites.Moreover,the rechargeable zinc-air battery in which both A-CoN_(3)S_(1)@C and IrO_(2)were simultaneously served as cathode catalysts(A-CoN_(3)S_(1)@C&IrO_(2))exhibits higher energy efficiency,larger power density,as well as better stability,compared to the commercial Pt/C&IrO_(2)-based zinc-air battery.The present result should be helpful for developing lower cost and higher performance ORR catalysts which is expected to be used in practical applications in energy devices.

Advances in gas sensors of tetrapyrrolato-rare earth sandwich-type complexes——Commemorating the 100th anniversary of the birth of Academician Guangxian Xu

In recent years,sandwich-type rare earth tetrapyrrole derivatives,have attracted more and more attention as material for conductimetric sensors.They have not only great chemical stability and processability,but also flexible molecular structure,which is a key to adjustable semiconductor properties.In this mini review,we focus mainly on the development of tetrapyrrolato-rare earth sandwich-type complexes as the semiconducting active layer in the gas sensors published in the last ten years(2010-2020).The main part includes two sections.In the single component gas sensing of sandwich rare earth tetrapyrrole complexes,we describe the influence factors of the single-component semiconducting active layer on the sensing performance of tetrapyrrolato-rare earth sandwich-type complexes,including substituents,central metals and π-conjugate systems.In the multi-component gas sensors,the synergistic effect between tetrapyrrolato-rare earth sandwich-type complex and other materials on improving sensitivity and conductivity has been discussed briefly.

Synthetic porphyrin chemistry in China

Porphyrins are a class of heterocyclic macrocycles,containing four pyrrolic subunits interconnected at theα-positions with four methine（=CH-）groups.

Chiral porphyrin assemblies

Porphyrins are among the most important macrocycles because they perform many essential functions in living systems and serve as building blocks in many functional materials.Incorporating the chirality into porphyrins can aid biomimetic research and the exploration of new functional materials.In this review,recent developments in chiral porphyrin assemblies are highlighted.The review is mainly divided into two sections:the different strategies for constructing chiral porphyrin assemblies and the applications.The formation of chiral porphyrin assemblies can be from porphyrin molecules substituted with chiral groups;achiral porphyrins induced by chiral additives and spontaneous deracemizations of achiral porphyrins during the assemblies.We also provide an overview of the applications of chiral porphyrin assemblies in chiral sensing,asymmetry catalysis,circularly polarized luminescence,and so on.The further challenge in the field is discussed.