Challenges and Opportunities in Preserving Key Structural Features of 3D-Printed Metal/Covalent Organic Framework

Metal-organic framework(MOF)and covalent organic framework(COF)are a huge group of advanced porous materials exhibiting attractive and tunable microstructural features,such as large surface area,tunable pore size,and functional surfaces,which have significant values in various application areas.The emerging 3D printing technology further provides MOF and COFs(M/COFs)with higher designability of their macrostructure and demonstrates large achievements in their performance by shaping them into advanced 3D monoliths.However,the currently available 3D printing M/COFs strategy faces a major challenge of severe destruction of M/COFs’microstructural features,both during and after 3D printing.It is envisioned that preserving the microstructure of M/COFs in the 3D-printed monolith will bring a great improvement to the related applications.In this overview,the 3D-printed M/COFs are categorized into M/COF-mixed monoliths and M/COF-covered monoliths.Their differences in the properties,applications,and current research states are discussed.The up-to-date advancements in paste/scaffold composition and printing/covering methods to preserve the superior M/COF microstructure during 3D printing are further discussed for the two types of 3D-printed M/COF.Throughout the analysis of the current states of 3D-printed M/COFs,the expected future research direction to achieve a highly preserved microstructure in the 3D monolith is proposed.

Controlled Assembly of Luminescent Lanthanide‑Organic Frameworks via Post‑Treatment of 3D‑Printed Objects

Complex multiscale assemblies of metal-organic frameworks are essential in the construction of largescale optical platforms but often restricted by their bulk nature and conventional techniques.The integration of nanomaterials and 3D printing technologies allows the fabrication of multiscale functional architectures.Our study reports a unique method of controlled 3D assembly purely relying on the post-printing treatment of printed constructs.By immersing a 3D-printed patterned construct consisting of organic ligand in a solution of lanthanide ions,in situ growth of lanthanide metal-organic frameworks(LnMOFs)can rapidly occur,resulting in macroscopic assemblies and tunable fluorescence properties.This phenomenon,caused by coordination and chelation of lanthanide ions,also renders a sub-millimeter resolution and high shape fidelity.As a proof of concept,a type of 3D assembled LnMOFsbased optical sensing platform has demonstrated the feasibility in response to small molecules such as acetone.It is anticipated that the facile printing and design approach developed in this work can be applied to fabricate bespoke multiscale architectures of functional materials with controlled assembly,bringing a realistic and economic prospect.

Bottom-up lithium growth guided by Ag concentration gradient in 3D PVDF framework towards stable lithium metal anode

Three-dimensional(3 D)frameworks have received much attention as an effective modification strategy for next-generation high-energy-density lithium metal batteries.However,the top-growth mode of lithium(Li)on the 3 D framework remains a tough challenge.To achieve a uniform bottom-up Li growth,a scheme involving Ag concentration gradient in 3 D PVDF framework(C-Ag/PVDF)is proposed.Ag nanoparticles with a concentration gradient induce an interface activity gradient in the 3 D framework,and this gradient feature is still maintained during the cycle.As a result,the C-Ag/PVDF framework delivers a long lifespan over 1800 h at a current density of 1 mA cm^(-2) with a capacity of 1 mAh cm^(-2),and shows an ultra-long life(>1300 h)even at a high current density of 4 mA cm^(-2) with a capacity of 4 mAh cm^(-2).The advantage of concentration gradient provides further insights into the optimal design of the 3 D framework for stable Li metal anode.

Atomic Modulation of 3D Conductive Frameworks Boost Performance of MnO2 for Coaxial Fiber‑Shaped Supercapacitors

Coaxial fiber-shaped supercapacitors are a promising class of energy storage devices requiring high performance for flexible and miniature electronic devices.Yet,they are still struggling from inferior energy density,which comes from the limited choices in materials and structure used.Here,Zn-doped CuO nanowires were designed as 3D framework for aligned distributing high mass loading of MnO2 nanosheets.Zn could be introduced into the CuO crystal lattice to tune the covalency character and thus improve charge transport.The Zn–CuO@MnO2 as positive electrode obtained superior performance without sacrificing its areal and gravimetric capacitances with the increasing of mass loading of MnO2 due to 3D Zn–CuO framework enabling efficient electron transport.A novel category of free-standing asymmetric coaxial fiber-shaped supercapacitor based on Zn0.11CuO@MnO2 core electrode possesses superior specific capacitance and enhanced cell potential window.This asymmetric coaxial structure provides superior performance including higher capacity and better stability under deformation because of sufficient contact between the electrodes and electrolyte.Based on these advantages,the as-prepared asymmetric coaxial fiber-shaped supercapacitor exhibits a high specific capacitance of 296.6 mF cm^−2 and energy density of 133.47μWh cm^−2.In addition,its capacitance retention reaches 76.57%after bending 10,000 times,which demonstrates as-prepared device’s excellent flexibility and long-term cycling stability.

3D Carbon Frameworks for Ultrafast Charge/Discharge Rate Supercapacitors with High Energy‑Power Density

Carbon-based electric double layer capacitors(EDLCs)hold tremendous potentials due to their high-power performance and excellent cycle stability.However,the practical use of EDLCs is limited by the low energy density in aqueous electrolyte and sluggish diffusion kinetics in organic or/and ionic liquids electrolyte.Herein,3D carbon frameworks(3DCFs)constructed by interconnected nanocages(10-20 nm)with an ultrathin wall of ca.2 nm have been fabricated,which possess high specific surface area,hierarchical porosity and good conductive network.After deoxidization,the deoxidized 3DCF(3DCFDO)exhibits a record low IR drop of 0.064 V at 100 A g^−1 and ultrafast charge/discharge rate up to 10 V s^−1.The related device can be charged up to 77.4%of its maximum capacitance in 0.65 s at 100 A g^−1 in 6 M KOH.It has been found that the 3DCF-DO has a great affinity to EMIMBF4,resulting in a high specific capacitance of 174 F g^−1 at 1 A g^−1,and a high energy density of 34 Wh kg^−1 at an ultrahigh power density of 150 kW kg^−1 at 4 V after a fast charge in 1.11 s.This work provides a facile fabrication of novel 3D carbon frameworks for supercapacitors with ultrafast charge/discharge rate and high energy-power density.

N/S co-doped 3D carbon framework prepared by a facile morphology-controlled solid-state pyrolysis method for oxygen reduction reaction in both acidic and alkaline media

Developing high-performance non-precious metal electrocatalysts for oxygen reduction reaction(ORR)is crucial for the commercialization of fuel cells and metal-air batteries.However,doped carbon-based materials only show good ORR activity in alkaline medium,and become less effective in acidic environment.We believe that an appropriate combination of both ionic and electronic transport path,and well dopant distribution of doped carbon-based materials would help to realize high ORR performance un-der both acidic and alkaline cond让ions.Accordingly,a nitrogen and sulfur co-doped carbon framework with hierarchical through-hole structure is fabricated by morphology-controlled solid-state pyrolysis of poly(aniline-co-2-ami no thiophenol)foam.The uniform high concentrations of nitrogen and sulfur,high intrinsic conductivity,and integrated three dimensional ionic and electronic transfer passageways of the 3D porous structure lead to synergistic effects in catalyzing ORR.As a result,the limiting current density of the carbonized poly(aniline-co-2-aminothiophenol)foam is equivalent to commercial Pt/C in acidic environment,and twice the latter in alkaline medium.

2D/2D S-scheme heterojunction with a covalent organic framework and g-C_(3)N_(4) nanosheets for highly efficient photocatalytic H2 evolution

The fabrication of S-scheme heterojunctions with fast charge transfer and good interface contacts,such as intermolecularπ–πinteractions,is a promising approach to improve photocatalytic performance.A unique two-dimensional/two-dimensional(2D/2D)S-scheme heterojunction containing TpPa-1-COF/g-C_(3)N_(4) nanosheets(denoted as TPCNNS)was developed.The established maximum interfacial interaction between TpPa-1-COF NS and g-C_(3)N_(4) NS may result in aπ–πconjugated heterointerface.Furthermore,the difference in the work functions of TpPa-1-COF and g-C_(3)N_(4) results in a large Fermi level gap,leading to upward/downward band edge bending.The spontaneous interfacial charge transfer from g-C_(3)N_(4) to TpPa-1-COF at theπ–πconjugated interface area results in the presence of a built-in electric field,according to the charge density difference analysis based on density functional theory calculations.Such an enhanced built-in electric field can efficiently drive directional charge migration via the S-scheme mechanism,which enhances charge separation and utilization.Thus,an approximately 2.8 and 5.6 times increase in the photocatalytic hydrogen evolution rate was recorded in TPCNNS-2(1153μmol g^(-1) h^(-1))compared to pristine TpPa-1-COF and g-C_(3)N_(4) NS,respectively,under visible light irradiation.Overall,this work opens new avenues in the fabrication of 2D/2Dπ–πconjugated S-scheme heterojunction photocatalysts with highly efficient hydrogen evolution performance.

A New 3-D Supramolecular Framework Built by Co4-Substituted Sandwiched Phosphotungstates, Organoamines and Co-Complexes: Synthesis, Structure, and Property

A neoteric organic-inorganic hybrid Co-substituted phosphotungstate H6{[Co(en)2(OAc)2]2[Co4(H2 O)2(PW9 O34)2]}?2 H2 en?36 H2 O(1, en = enthylenediamine) has been made under hydrothermal conditions and characterized by IR spectrum, thermogravimetric analysis, diffuse-reflectance spectroscopy, powder X-ray diffraction, single-crystal X-ray diffraction and cyclic voltammetry, respectively. Crystal data for 1: monoclinic, P21/c, a = 18.2234(12), b = 15.3696(9), c = 20.1706(17) ?, β = 106.563(8)°, V = 5415.1(7) ?3, Z = 2, Mr = 6072.30, Dc = 3.724 g/cm3, μ = 20.087 mm-1, F(000) = 5540, R = 0.0585, w R = 0.1543 and S = 1.024. Single-crystal X-ray structure analysis reveals that compound 1 exhibits a 3-D supramolecular framework via H-bonding interactions, in which the discrete Co-complex is modified by two types of organic ligands, en and acetate. In addition, the adsorption experiments demonstrate compound 1 possesses a remarkable capability for scavenging of methylene blue.

Hydrothermal Synthesis and Structural Characterization of a Novel 3-D Open Framework Zinc Phosphate Microporous Compound(C_5N_2H_(14))·[Zn_3(OH_2)(PO_4)_2(HPO_4)]

One novel organically templated zincophophate （CsN2HI4）.[Zn3（OH2）（POn）2（HPO4）] has been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction together with elemental analysis, infrared spectroscopy, thermogravimetric analysis, and powder X-ray diffraction. The title compound crystallizes in the monoclinic space group P21/n, with a = 9.7904（11）, b = 14.0287（14）, c = 11.8651（13） A, β= 104.690（3）°, V= 1576.4（3） A^3, Z= 4, T= 296（2） K, Mr = 601.31 and Dc = 2.533 g/cm^3. The compound consists of a macroanionic [Zn3（OH2）（PO4）2（HPO4）]^2- framework and （C5N2H14）^2＋ cations, and its structure is built up from ZnO3（OH2）, ZnO4, HPO4 and PO4 tetrahedral units that result in 4, 8 and 10-ring channels.

Synthesis and Crystal Structure of an Interpentateing 3-D Framework Constructed from Mixed Ligands

A novel organic-inorganic hybrid compound constructed from mixed ligands, Co3（SIP）2（bipy）4（H2O）6·6.5H2O （H3SIP = 5-sulfoisophthalic acid, bipy = 4,4′-bipyridyl）, has been hydrothermally synthesized and characterized by IR, TGA and single-crystal X-ray diffraction. The crystal belongs to orthorhombic, space group P212121 with a = 11.395（2）, b = 19.395（4）, c = 30.675（6） A^°, Mr = 1513.05, V= 6779（2） A^°^3, Dc= 1.482 g/cm^3, F（000） = 3120, μ = 0.873 mm^-1, Z= 4, the final R = 0.0439 and wR = 0.119 for 13421 observed reflections with I〉 2σ（I）. The structure of the compound presents a 3-D framework containing Co-bipy 1-D chain and 2-D bilayer motifs and carboxylate spacers, and the connection of 1-D chain and 2-D bilayer motifs by carboxylate ligand results in the final open framework with twofold interpenetration net. A probe reaction of the oxidation of benzaldehyde with H2O2 using the title compound as catalyst was carded out in a liquid-solid system, showing that the compound has high oxidative catalytic activity to the reaction.

One New 3D Pillared-layer Ag(Ⅰ)-Coordination Framework Based on a Unique 1D Ag2O2 Ribbon： Synthesis,Crystal Structure and Luminescent Properties

A new 3D Ag（I） coordination polymer {[Ag（AZDB）（0.5）（bpe）（0.5）]·H2O}n（1） has been papared by azobenzene-3,3？-dicarboxylicate（H2AZDB）, 1,2-bis（4-pyridyl）ethylene（bpe） and silver salts via hydrothermal method. The compound was fully characterized by single-crystal X-ray diffraction, elemental analyses, infrared spectrum（IR）, powder X-ray diffraction（PXRD） and thermogravimetric analysis（TGA）. The strucrural analysis indicate that compound 1 shows a 3D pillared-layer framework constructed from a unique 1D Ag2O2 ribbon and pyridyl/carboxylicate mixed system, which features a 2-nodal（4, 6）-connected fsc net with a（4^4·6^10·8）（4^4·6^2） topology.Moreover, the photoluminescent properties have also been discussed.

Keggin型硅钨酸盐[Cu(dap)_2(H_2O)][Cu(dap)_2][Na(H_2O)_5]H[SiW_(11)CuO_(39)]·H_2O的合成与结构(英文)

在水热条件下,以Na10[A-α-SiW9O34].18H2O、氯化铜、四氮唑乙酸和1,2-丙二胺为原料合成了一种三维有机-无机杂化单铜取代Keggin型硅钨酸盐[Cu(dap)2(H2O)][Cu(dap)2][Na(H2O)5]H[α-SiW11CuO39].H2O(1),并借助元素分析、红外光谱和单晶X射线衍射对其进行了表征.结果表明,化合物1的分子结构片段由1个单铜取代Keggin型多金属氧酸盐单元[α-SiW11CuO39]6-,1个支撑的[Cu(dap)2(H2O)]2+配离子,1个[Cu(dap)2(H2O)]2+桥配离子,1个[Na(H2O)5]+离子和1个结晶水分子组成.在[α-SiW11CuO39]6-单元中,缺位位点完全被一个铜原子占据,而不是被半个铜原子和半个钨原子所占据.值得注意的是,每个分子结构片段与4个邻近相同片段相连构筑有机-无机杂化三维框架.

Three dimensional porous frameworks for lithium dendrite suppression

Lithium metal is a promising anode material owing to its very low electrochemical potential and ultrahigh specific capacity.However,the growth of lithium dendrites could result in a short lifespan,low coulombic efficiency,and potential safety hazards during the progress of lithium plating/stripping.These factors drastically hinder its application in lithium metal batteries.This review focuses on the use of three dimensional(3D)porous host frameworks to improve Li plating/stripping behaviors,accommodate the change in volume,and suppress or block lithium dendrite growth.Various 3D porous frameworks,including the conductive carbon-based,metal-based,and lithiophilic inorganic-compound frameworks are introduced and summarized in detail.The particular functions,relative developments,and optimized strategies of various 3D porous frameworks for lithium deposition/dissolution behaviors are discussed.Moreover,the challenges and promising developments in the field of Li metal anodes will be discussed at the end of this review.

Weaving 3D highly conductive hierarchically interconnected nanoporous web by threading MOF crystals onto multi walled carbon nanotubes for high performance Li-Se battery

Lithium-selenium(Li-Se)battery has attracted growing attention.Nevertheless,its practical application is still impeded by the shuttle effect of the formed polyselenides.Herein,we report in-situ hydrothermal weaving the three-dimensional(3 D)highly conductive hierarchically interconnected nanoporous web by threading microporous metal organic framework MIL-68(Al)crystals onto multi-walled carbon nanotubes(MWCNTs).Such 3 D hierarchically nanoporous web(3 D MIL-68(Al)@MWCNTs web)with a very high surface area,a large amount of micropores,electrical conductivity and elasticity strongly traps the soluble polyselenides during the electrochemical reaction and significantly facilitates lithium ion diffusion and electron transportation.Molecular dynamic calculation confirmed the strong affinity of MIL-68(Al)for the adsorption of polyselenides,quite suitable for Li-Se battery.Their hexahedral channels(1.56 nm)are more efficient for the confinement of polyselenides and for the diffusion of electrolytes compared to their smaller triangular channels(0.63 nm).All these excellent characteristics of 3 D MIL-68(Al)@MWCNTs web with suitable confinement of a large amount of selenium and the conductive linkage between MIL-68(Al)host by MWCNTs result in a high capacity of 453 m Ah/g at 0.2 C with 99.5%coulombic efficiency after 200 cycles with significantly improved cycle stability and rate performance.The 3 D MIL-68(Al)@MWCNTs web presents a good performance in Li-Se battery in term of the specific capacity and cycling stability and also in terms of rate performance compared with all the metal-organic framework(MOF)based or MOF derived porous carbons used in Li-Se battery.

Revisiting the Role of Physical Confinement and Chemical Regulation of 3D Hosts for Dendrite-Free Li Metal Anode

Lithium metal anode has been demonstrated as the most promising anode for lithium batteries because of its high theoretical capacity,but infinite volume change and dendritic growth during Li electrodeposition have prevented its practical applications.Both physical morphology confinement and chemical adsorption/diffusion regulation are two crucial approaches to designing lithiophilic materials to alleviate dendrite of Li metal anode.However,their roles in suppressing dendrite growth for long-life Li anode are not fully understood yet.Herein,three different Ni-based nanosheet arrays(NiO-NS,Ni_(3)N-NS,and Ni_(5)P_(4)-NS)on carbon cloth as proof-of-concept lithiophilic frame-works are proposed for Li metal anodes.The two-dimensional nanoarray is more promising to facilitate uniform Li^(+)flow and electric field.Compared with the NiO-NS and the Ni_(5)P_(4)-NS,the Ni_(3)N-NS on carbon cloth after reacting with molten Li(Li-Ni/Li_(3)N-NS@CC)can afford the strongest adsorption to Li+and the most rapid Li+diffusion path.Therefore,the Li-Ni/Li_(3)N-NS@CC electrode realizes the lowest overpotential and the most excellent electrochemical performance(60 mA cm^(−2)and 60 mAh cm^(−2)for 1000 h).Furthermore,a remarkable full battery(LiFePO_(4)||Li-Ni/Li_(3)N-NS@CC)reaches 300 cycles at 2C.This research provides valuable insight into designing dendrite-free alkali metal batteries.

Three-dimensional paper-like graphene framework with highly orientated laminar structure as binder-free supercapacitor electrode

A free-standing paper-like three-dimensional graphene framework（3DGF） with orientated laminar structure and interconnected macropores, was obtained by the hard template-directed ordered assembly. As the sacrificial templates, polystyrene（PS） latex spheres were assembled with graphene oxide（GO） to build up a sandwich type composite film, followed by heat removal of which with a simultaneous reduction of GO. The 3DGF exhibited high specific surface area of 402.5 m2/g, controllable pores and mechanical flexibility, which was employed as the binder-free supercapacitor electrode and shows high specific gravimetric capacitance of 95 F/g at 0.5 A/g, with enhanced rate capability in 3 electrode KOH system.

A 3D conducting scaffold with in-situ grown lithiophilic Ni_(2)P nanoarrays for high stability lithium metal anodes

Lithium(Li)metal is the most potential anode material for the next-generation high-energy rechargeable batteries.However,intrinsic surface unevenness and‘hostless’nature of Li metal induces infinite volume effect and uncontrollable dendrite growth.Herein,we design the in-situ grown lithiophilic Ni_(2)P nanoarrays inside nickel foam(PNF).Uniform Ni_(2)P nanoarrays coating presents a very low nucleation overpotential,which induces the homogeneous Li deposition in the entire spaces of three-dimensional(3D)metal framework.Specifically,the lithiophilic Ni_(2)P nanoarrays possess characteristics of electrical conductivity and structural stability,which have almost no expansion and damage during repeating Li plating/stripping.Therefore,they chronically inhibit the growth of Li dendrites.This results in an outstanding Coulombic efficiency(CE)of 98% at 3 mA cm^(-2) and an ultra long cycling life over 2000 cycles with a low overpotential.Consequently,the PNF-Li||LiFePO_(4) battery maintains a capacity retention of 95.3% with a stable CE of 99.9% over 500 cycles at 2 C.

Synthesis, Structure, and Luminescent Property of a 3-D Strontium Complex [Sr_3(pda)_2(Hpda)_2(H2O)_2]_n·2nH_2O

The title complex [Sr3（pda）2（Hpda）2（H2O）2]n·2nH2O（H2pda = pyridine-2,6-dicar- boxylic acid） has been prepared under solvothermal conditions. It has been characterized by X-ray single-crystal diffraction, IR and elemental analysis. The crystal belongs to the monoclinic system, space group P21/c with a = 10.3795（8）, b = 9.2225（7）, c = 18.5726（14） , β = 104.377（2）o, V = 1722.2（2） 3, C28H22N4O20Sr3, Mr = 997.36, Z = 2, Dc = 1.923 g/cm3, μ = 4.722 mm-1, F（000） = 984, the final R = 0.0269 and wR = 0.0538. This complex possesses a 3-D structure which is constructed from 1-D chain motifs linked by carboxylate groups. The luminescent property of the title complex has been investigated.

Synthesis,Structure,and Luminescent Property of a 3-D Zinc Complex {[Zn_8^(II)(4-APha)_8(CH_3COO)_8](CH_3CH_2OH)_2}_n

The title complex [ZN8II（4-APha）8（CH3COO）8（CH3CH2OH）2]n （1, 4-APha = 4-ami- nophenylhydroxamic acid） has been prepared under solvothermal conditions. It has been characterized by X-ray single-crystal diffraction, IR and elemental analysis. The crystal belongs to the monoclinic system, space group C2/c with a = 39.074（4）, b = 9.9645（8）, c=38.846（3） A, β = 136.438°, V= 10423.1（14） A3, C84H118N16O39Zn8, Mr = 2498.90, Z = 4, Dc = 1.592 g/cm3,μ= 1.900 mm-1, F（000） = 5144, the final R = 0.1036 and wR = 0.2953. This complex possesses a 3-D structure which is constructed from 1-D chain motifs linked by the 4-APha＂ ligands. The luminescent property of the title complex has been investigated.

A Novel 3D Cobalt(II) Complex Constructed by 2,2'-(1,4-Butanediyl)bis(1H-benzimidazole) Ligand

A novel 3D polymer 1 （C26H22CoN4O4, Mr = 513.41） constructed from H2C4BIm （2,2＇-（1,4-butanediyl）bis（1H-benzimidazole）], 1,3-bdc （1,3-benzenedicarboxylate） and Co（II） has been successfully synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction analysis. The crystal belongs to the tetragonal system, space group I-42d with a = 24.315（5）, b = 24.315（5）, c = 8.343（2）, V = 4933（2）3, Z = 8, Dc = 1.383 g/cm3, μ（MoKα） = 0.735 mm-1, F（000） = 2120, S = 1.156, the final R = 0.0596 and wR = 0.1346 for 1529 reflections with I 2σ（I）. Complex 1 contains 1D chains which are connected by extensive hydrogen-bonding interactions to form the 2D folded layer and 3D framework, which also stabilize the structure.