Different Routes to the Pore Engineering of Spherical MCM-41

Different routes,including the replacements of the template,addition of pore expander and hydrothermal post-synthesis treatment have been used for the pore engineering of spherical MCM-41.A comparison among the pore engineering effects of these methods has been made.The results show that the hydrothermal post-synthesis treatment affords the synthesized material with a larger pore size and narrow pore size distribution without changing the spherical morphology.As far as the pore-size expansion is concerned,the addition of DMTA is the most effective one,but this might be limited by the spherical morphology.Combining the replacement of C 16TMABr with the Gemini surfactant GEM 16-8-16 with an addition of DMTA gives rise to the largest pore volume and surface area.

Pore Engineering for Covalent Organic Framework Membranes

Membrane technology is of particular significance for the sustainable development of society owing to its potential capacity to tackle the energy shortage and environmental pollution.Membrane materials are the core part of membrane technology.Researchers have always been pursuing predictable structures of advanced membrane materials,which provides a possibility to fully unlock the potential of membranes.Covalent organic frameworks(COFs),with the advantage of controllable pore microenvironment,are considered to be promising candidates to achieve this design concept.The customizable function of COF membranes through pore engineering does well in the enhancement of selective permeability performance,which offers COF membranes with great application potentials in separation and transportation fields.In this context,COF-based membranes have been developed rapidly in recent years.Herein,we present a brief overview on the strategies developed for pore engineering of COF membranes in recent years,including skeleton engineering,pore surface engineering,host-guest chemistry and membrane fabrication.Moreover,the features of transmission or separation of molecules/ions based on COF membranes and corresponding applications are also introduced.In the last part,the challenges and prospects of the development of COF membranes are discussed.

Engineering two-dimensional pores in freestanding TiO_2/graphene gel film for high performance lithium ion battery

As the key component of electrochemical energy storage devices, an electrode with superior ions transport pores is the important premise for high electrochemical performance. In this paper, we developed a unique solution process to prepare freestanding TiO_2/graphene hydrogel electrode with tunable density and porous structures. By incorporating room temperature ionic liquids（RTILs）, even upon drying, the non-volatile RTILs that remained in the gel film would preserve the efficient ion transport channels and prevent the electrode from closely stacking, to develop dense yet porous structures. As a result, the dense TiO_2/graphene gel film as an electrode for lithium ion battery displayed a good gravimetric electrochemical performance and more importantly a high volumetric performance.

Efficient Splitting of Trans-/Cis-Olefins Using an Anion-Pillared Ultramicroporous Metal-Organic Framework with Guest-Adaptive Pore Channels

Trans-/cis-olefin isomers play a vital role in the petrochemical industry.The paucity of energy-efficient technologies for their splitting is mainly due to the similarities of their physicochemical properties.Herein,two new tailor-made anion-pillared ultramicroporous metal–organic frameworks(MOFs),ZU-36-Ni and ZU-36-Fe(GeFSIX-3-Ni and GeFSIX-3-Fe)are reported for the first time for the efficient trans-/cis-2-butene(trans-/cis-C_(4)H_(8))mixture splitting by enhanced molecular exclusion.Notably,ZU-36-Ni unexpectedly exhibited smart guest-adaptive pore channels for trapping trans-C_(4)H_(8)with a remarkable adsorption capacity(2.45 mmol∙g^(−1))while effectively rejecting cis-C_(4)H_(8)with a high purity of 99.99%.The dispersion-corrected density functional theory(DFT-D)calculation suggested that the guest-adaptive behavior of ZU-36-Ni in response to trans-C_(4)H_(8)is derived from the organic linker rotation and the optimal pore dimensions,which not only improve the favorable adsorption/diffusion of trans-C_(4)H_(8)with optimal host–guest interactions,but also enhance the size-exclusion of cis-C_(4)H_(8).This work opens a new avenue for pore engineering in advanced smart or adaptive porous materials for specific applications involving guest molecular recognition.

Bi-/multi-modal pore formation of PLGA/hydroxyapatite composite scaffolds by heterogeneous nucleation in supercritical CO_2 foaming

Scaffolds with multimodal pore structure are essential to cells differentiation and proliferation in bone tissue engineering. Bi-/multi-modal porous PLGA/hydroxyapatite composite scaffolds were prepared by supercritical C02 foaming in which hydroxyapatite acted as heterogeneous nucleation agent. Bimodal porous scaffolds were prepared under certain conditions, i.e. hydroxyapatite addition of 5%, depressurization rate of 0.3 MPa. min-1, soaking temperature of 55 ℃, and pressure of 9 MPa. And scaffolds presented specific structure of small pores （122 μM ± 66 μm） in the cellular walls of large pores （552 μm ±127 μm）. Furthermore, multimodal porous PLGA scaffolds with micro-pores （37 μM ± 11μM） were obtained at low soaking pressure of 7.5 MPa. The interconnected porosity of scaffolds ranged from （52.53 ± 2.69）% to （83.08±2.42）% by adjusting depressurization rate, while compression modulus satisfied the requirement of bone tissue engineering. Solvent-free CO2 foaming method is promising to fabricate bi-/multi-modal porous scaffolds in one step, and bioactive particles for osteogenesis could serve as nucleation agents.

A topology approach to overcome the pore size/volume trade-offs for autonomous indoor humidity control

Autonomous indoor humidity control is gaining more and more attention but is limited by the trade-offs among pore volume,pore size and water stability of water adsorbents.We solve this problem by using a unique coordination network topology combined with hydrolytically stable M(Ⅲ)carboxylate clusters.By extending the ligand length from 9.0 to 11.2 and 13.7?,the pore volume significantly increases from 0.99 to 1.40 and 1.78 cm^(3)g^(-1),which proportionally increases the saturated water adsorption capacity.Meanwhile,the pore size slightly increases from 10.4 to 11.0 and 13.5A,which restricts the isotherm inflection pressure and hysteresis width to meet the requirement of indoor humidity control.Large single-crystals suitable for Xray diffraction studies were obtained by using Fe(Ⅲ)salts,while isostructural frameworks with sufficiently high water stabilities were synthesized by using Cr(Ⅲ)salts,which offer record working capacity of 0.90 and 1.10 g g^(-1)for indoor humidity control.

Pore-Directed Solid-State Selective Photoinduced E–Z Isomerization and Dimerization within Metal–Organic Frameworks

Design and construction of suitable pore microenvironments for selective catalytic reactions of small guest molecules is a major goal for chemists.Herein,we report control of competitive E–Z photoisomerization and photodimerization within porous metal–organic frameworks(MOFs)by fine-tuning the pore microenvironments using different dicarboxylate linkers.MOFs with small pores((E)-X_(MOF_(1))and(E)-X_(MOF_(1))′)favor the photoinduced E–Z isomerization of one encapsulated diaryl alkene substrate while those with large pores(((E)-X)_(2MOF_(2)))prefer the photodimerization of two encapsulated alkene substrates.Both reactions show broad functional group compatibility and proceed stereospecifically in good yields under mild conditions.High local concentration of diaryl alkene ligands and their preorientation within pores facilitate stereoselective dimerization.This pore engineering strategy is applicable to control and create pore microenvironemnts for other photoinduced organic reactions within porous MOFs.

Dynamic Spacer Installation of Multifunctionalities into Metal-Organic Frameworks for Spontaneous One-Step Ethylene Purification from a Ternary C_(2)-Hydrocarbons Mixture

Simultaneous ethane and acetylene removal from a C_(2)-gases mixture(C_(2)H_(6),C_(2)H_(4),and C_(2)H_(2))through a one-step separation process for ethylene purification is of great importance yet challenging in petrochemical industry,owing to their similar molecule sizes and physical properties.Herein,a series of multifunctionalized metal–organic frameworks(MOFs),LIFM-XYY-1∼8(LIFM stands for Lehn Institute of Functional Materials,and XYY are the initials of the first author),are constructed via a dynamic spacer installation(DSI)approach to optimize the pore-nanospaces for efficient C_(2)H_(4) isolation from the ternary C_(2)-gases mixture.Installation of variable organic-spacers into the prototypical MOFs,LIFM-28 or PCN-700,results in dramatically improved pore volume/surface area,contracted pore size,and functionalized pore surface,which in turn bring out high C_(2)-gases uptake capacities,enhanced C_(2)H_(6) and C_(2)H_(2) adsorption selectivities over C_(2)H_(4),and fast adsorption kinetics,providing an effective strategy to achieve delicate trade-off among these indexes for adequate separation performance.Specifically,optimized LIFM-XYY-7 presents four-times C_(2)H_(6) and C_(2)H_(2) adsorption capacities than proto-PCN-700.Dynamic breakthrough experiments reveal that poly-grade C_(2)H_(4)(>99.9%)can be obtained from binary or ternary C_(2)-hydrocarbon mixtures through a single separation process.Combined with themolecular simulations,this work demonstrates a promising protocol of porenanospace engineering via multi-functional optimization by the DSI approach to screen out MOFs for a formidable task.

Ultrathin 2D Covalent Organic Framework Film Fabricated via Langmuir-Blodgett Method with a“Two-in-One”Type Monomer

In recent years, covalent organic frameworks(COFs) are evolving as a novel kind of porous materials for catalysis and molecular separation, gas adsorption, etc. Various functional building blocks have been explored to tune the pore channels, including the pore size and structures. In this article, a new terphenyl(TP) based COF(TP-COF) was developed via a “two-in-one” strategy by using a symmetric A2B2monomer, i.e., 4,4''-diamino-2',5'-diformyl-1,1':4',1''-terphenyl(DADFTP). The pore size of TP-COF was only 0.99 nm by shortening the arm length of the DADFTP monomer. Freestanding, continuous and ultrathin COF films could be facilely prepared at the air-liquid interface through the modified Langmuir-Blodgett(LB) method. TP-COF films exhibited high rejection of over 90% for dyes removal.

Lithium Ion Conduction in Covalent Organic Frameworks

Ion conduction plays key roles in electrochemical systems,including fuel cells,lithium ion batteries,and metal-air batteries.Covalent organic frameworks(COFs),as a new class of porous polymers,constructed by pre-designable building blocks,are ideal hosts to accommodate ionic carries for conduction because of their straightforward pore channels,tunable pore size,controllable pore environment,and good chemical and thermal stability.Different from proton conduction,how to achieve high lithium ion conduction is still a challenge as it is difficult to dissociate ionic bonds of the lithium salts.To facilitate the dissociation of lithium salts,COFs with different pores and skeletons are well designed and constructed.This review focuses on emerging developments of lithium ion conduction in COFs,and discusses the structures of these COFs and conductive performance to elucidate the structure-property correlations.Furthermore,we have concluded the remaining challenge and future direction in these COF-based lithium conductive areas.This review provides deeper insight into COFs for ionic conduction.