Technological application of the electrochemical reduction of CO_(2)relies on efficient electrocatalysts.We demonstrate that the introduction of amino groups alongside the porphyrin cobalt centers in a metal-organic f...Technological application of the electrochemical reduction of CO_(2)relies on efficient electrocatalysts.We demonstrate that the introduction of amino groups alongside the porphyrin cobalt centers in a metal-organic framework(MOF)can dramatically accelerate the electrochemical CO_(2)reduction performance.A classic cobalt porphyrin-based MOF showing moderate CO_(2)-to-CO electroreduction performance(turnover frequency[TOF]=0.20 s^(−1),Faradic efficiency[FE]=47.4%)is modified.By molecular design of the porphyrin-based ligand,amino groups are introduced alongside the cobalt center,giving remarkably enhanced CO_(2)-to-CO electroreduction performance as high as FE 99.4%,current density 7.2 mA cm^(−2),and TOF 21.17 s^(−1),in a nearneutral aqueous solution at a low overpotential of 525 mV.Density functional theory calculations showed that the prepositioned amino groups,although located not sufficiently close to the active center,serve as hydrogen-bonding donors to stabilize the intermediate Co-CO_(2)adduct and impede the formation of Co-H_(2)O adduct,which not only promotes the CO_(2)reduction reaction but also restrains the hydrogen evolution reaction.展开更多
Two-dimensional (2D) materials and ultrathin nanosheets have attracted tremendous research interests [1-4]. Exfoliation of porous coordination polymers (PCPs) or metal-organic frameworks (MOFs) with 2D coordination st...Two-dimensional (2D) materials and ultrathin nanosheets have attracted tremendous research interests [1-4]. Exfoliation of porous coordination polymers (PCPs) or metal-organic frameworks (MOFs) with 2D coordination structures is emerging as a viable strategy for preparation of new types of 2D materials [5-8]. The relatively weak bonding within and strong interactions between 2D coordination networks are the main problems for successful exfoliation [9]. Pretreatments of the layered MOFs to expand the interlayer distances can be helpful [10-12]. Capturing the exfoliation intermediates and visualizing their structures are valuable for understanding the exfoliation mechanism and confirming the structures of the final 2D materials [11,12].展开更多
Understanding,controlling,and utilizing the flexibility of adsorbents are of great importance and difficulty.Analogous with conventional solid materials,downsizing to the nanoscale is emerging as a possible strategy f...Understanding,controlling,and utilizing the flexibility of adsorbents are of great importance and difficulty.Analogous with conventional solid materials,downsizing to the nanoscale is emerging as a possible strategy for controlling the flexibility of porous coordination polymers(or metal-organic frameworks).We report a unique flexibility controllable by crystal size at the micrometer to submillimeter scale.Template removal transforms[Cu_(2)(pypz)_(2)]·0.5p-xylene(MAF-36,Hpypz=4-(1H-pyrazol-4-yl)pyridine)with one-dimensional channels toα-[Cu_(2)(pypz)_(2)]with discrete small cavities,and further heating gives a nonporous isomerβ-[Cu_(2)(pypz)_(2)].Both isomers can adsorb p-xylene to give[Cu_(2)(pypz)_(2)]·0.5p-xylene,meaning the coexistence of guest-driven flexibility and shape-memory behavior.The phase transition temperature fromα-[Cu_(2)(pypz)_(2)]toβ-[Cu_(2)(pypz)_(2)]decreased from~270℃ to~150℃ by increasing the crystal size from the micrometer to the submillimeter scale,ca.2-3 orders larger than those of other size-dependent behaviors.Single-crystal X-ray diffraction showed coordination bond reconstitution and chirality inversion mechanisms for the phase transition,which provides a sufficiently high energy barrier to stabilize the metastable phase without the need of downsizing to the nanoscale.By virtue of the crystalline molecular imprinting and gate-opening effects,α-[Cu_(2)(pypz)_(2)]andβ-[Cu_(2)(pypz)_(2)]show unprecedentedly high p-xylene selectivities of 16 and 51,respectively,as well as ultrafast adsorption kinetics(<2 minutes),for xylene isomers.展开更多
Adsorptive separation of p-xylene(pX)from xylene isomers is a key process in chemical industry,but known adsorbents cannot simultaneously achieve high adsorption selectivity,capacity,and rate.Here,we demonstrate gatin...Adsorptive separation of p-xylene(pX)from xylene isomers is a key process in chemical industry,but known adsorbents cannot simultaneously achieve high adsorption selectivity,capacity,and rate.Here,we demonstrate gating ultramicropore as a solution for this challenge.Slight modification of the synthetic condition gives rise to isomeric metal-organic frameworksα-[Zn(pba)](MAF-88,H2pba=4-(1H-pyrazol-4-yl)benzoic acid)andβ-[Zn(pba)](MAF-89)possessing similar pillared-column structures,porosities,and high pX capacities of 2.0 mmol g^(−1),but very different framework/pore topologies,pore sizes,and pX selectivities.For binary and ternary mixtures of liquid xylene isomers,MAF-88 with narrow one-dimensional(1D)channels shows pX selectivity of 11 and 1.6,while MAF-89 with 3D-connected quasi-discrete pores shows pX selectivity up to 221 and 46,respectively.Thermogravimetry,differential scanning calorimetry,and time-dependent separation experiments reveal that the kinetic effects of the gating pores play more important roles than the thermodynamic effects,which is further confirmed by single-crystal X-ray diffraction and computational simulations.展开更多
Solvothermal reactions of 3,6-di(pyridin-4-yl)-9H-carbazole(dpc)with Cu(ll)yielded crystals of two new coordination complexes,namely[Cu(CH_(3)COO)_(2)(dpc)(H_(2)O)_(2)]n-xGuest(1)and[Cu_(13)(HCOO)_(16)(dpc)16(H_(2)O)6...Solvothermal reactions of 3,6-di(pyridin-4-yl)-9H-carbazole(dpc)with Cu(ll)yielded crystals of two new coordination complexes,namely[Cu(CH_(3)COO)_(2)(dpc)(H_(2)O)_(2)]n-xGuest(1)and[Cu_(13)(HCOO)_(16)(dpc)16(H_(2)O)6](HCOO)10-Guest(2),in which CH_(3)COO_and HCOO-were generated from the hydrolysis of the solvents A/zAZ-dimethylacetamide(DMA)and A/zA/-dimethylformamide(DMF),respectively.Single-crystal X-ray diffraction showed that 1 possesses simple wavy coordination chains,while 2 possesses large molecular bowls/sieves with outer and inner effective sizes of 30.2 × 30.2 × 25.5 A^(3) and 15.0 × 15.0 × 18.6 A^(3),respectively,which consists of 4 linear Cu_(3)(HCOO)_(4)(H_(2)O)clusters and 12 dpc ligands as the square-shaped wall and a claw-like Cu(dpc)_(4) fragment as the bottle.Guest-free 2 can adsorb considerable amounts of CO_(2)/H_(2)O and CH_(3)OH but completely exclude C2H4 and C3H6z which shows a potential application for olefin drying.展开更多
Solvothermal reaction of Zn(NO_3)_2, 4-(1H-pyrazol-4-yl)pyridine(Hpypz) and 1,3,5-benzenetricarboxylic acid(H_3btc) in N,N-dimethylacetamide(DMA) produced a new porous coordination polymer [Zn_5(pypz)_4(btc)_2](1). Si...Solvothermal reaction of Zn(NO_3)_2, 4-(1H-pyrazol-4-yl)pyridine(Hpypz) and 1,3,5-benzenetricarboxylic acid(H_3btc) in N,N-dimethylacetamide(DMA) produced a new porous coordination polymer [Zn_5(pypz)_4(btc)_2](1). Single-crystal X-ray diffraction study of 1 showed that deprotonated pypz~– ligands served as 1,2,4-triazolate-like ligands, linking Zn(II) ions to form porous two-dimensional(2-D) sql-a layers {Zn(pypz)}^+, which were further connected by eight-legged pillars {Zn_2(btc)_4(H_2O)_2}^(8–) based on the typical paddlewheel dinuclear Zn_2(RCOO)_4(H_2O)_2 cluster to form a novel type of non-interpenetrated pillared-layer framework with 3-D intersecting pore system and large pore volume. Gas sorption measurements revealed that 1 possesses large BET surface area of 2061 m^2 g^(–1) and very high methane total uptake of 245 cm^3(STP) cm^(–3) at 298 K and 65 bar.展开更多
Hydrophobic ethyl, butyl or hexyl groups were introduced into the dicarboxylate ligand in the fluorescent porous coordination framework [Zn_2(fda)_2(bpy)](LMOF-202, H_2fda=9H-fluorene-2,7-dicarboxylic acid, bpy=4,4′-...Hydrophobic ethyl, butyl or hexyl groups were introduced into the dicarboxylate ligand in the fluorescent porous coordination framework [Zn_2(fda)_2(bpy)](LMOF-202, H_2fda=9H-fluorene-2,7-dicarboxylic acid, bpy=4,4′-bipyridine) for improving water stability and tuning oxygen sensitivity. The long hexyl groups gave satisfactory water stability but its oxygen sensitivity is low(70.8% fluorescence quenched at 1 bar O_2(1 bar=105 Pa)). In contrast, the shorter side groups gave high oxygen sensitivity(93.9% fluorescence quenched at 1 bar O_2) and low water stability. The derivation of the Stern-Volmer curves of the O_2 luminescence quenching data from the linear form can be used for detecting trace impurities in the luminescent framework, being much more sensitive than conventional methods such as powder X-ray diffraction. Mixing the ethyl and hexyl groups in the solid-solution manner brought high oxygen sensitivity(96.4% fluorescence quenched at 1 bar O_2) and high water stability simultaneously in the same coordination framework.展开更多
Controlling interpenetration and flexibility behaviors is intriguing and fundamental for porous coordination polymers.We report exceptional interpenetration behaviors involving controllable partial order–disorder str...Controlling interpenetration and flexibility behaviors is intriguing and fundamental for porous coordination polymers.We report exceptional interpenetration behaviors involving controllable partial order–disorder structural transformations.A new bis-benzotriazolate ligand(NaH2sbbta)with a twisted and anionic backbone was designed and synthesized.The solvothermal reaction of ZnCl_(2) and NaH_(2)sbbta yielded(Et_(2)NH_(2))_(3)[Zn_(5)Cl_(4)(sbbta)_(3)]·6DEF(2)possessing two-fold interpenetrated anionic pcu networks with symmetry,shape,and charge different from the known analogues.More interestingly,powder and single-crystal X-ray diffractions showed that 2 can undergo solvent-induced structural transformation to form a noninterpenetrated anionic pcu network with larger pores(1).Consequently,1/2 can selectively adsorb/exchange cationic dyes fromneutral and anionic dyes with tunable size selectivity.However,since the transformations are reversible without obvious change of crystal sizes,the network that disappeared in X-ray crystallography should be mainly disordered rather than decomposed.Further,the structural transformations can be suppressed by thermal decomposition/removal of Et_(2)NH_(2)^(+)/Et_(2)NH.Computational simulations indicate that the ordered and disordered structures are stabilized by relatively large and small solvent molecules,respectively.展开更多
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 coordi...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.展开更多
基金This research was supported by the National Key Research and Development Program of China(grant no.2021YFA1500401)the National Natural Science Foundation of China(grant nos.21890380,21821003,22071272,21975290,and 21731007)+1 种基金the Guangdong Pearl River Talents Program(grant no.2017BT01C161)the Guangdong Natural Science Funds for Distinguished Young Scholar(grant no.2018B030306009).
文摘Technological application of the electrochemical reduction of CO_(2)relies on efficient electrocatalysts.We demonstrate that the introduction of amino groups alongside the porphyrin cobalt centers in a metal-organic framework(MOF)can dramatically accelerate the electrochemical CO_(2)reduction performance.A classic cobalt porphyrin-based MOF showing moderate CO_(2)-to-CO electroreduction performance(turnover frequency[TOF]=0.20 s^(−1),Faradic efficiency[FE]=47.4%)is modified.By molecular design of the porphyrin-based ligand,amino groups are introduced alongside the cobalt center,giving remarkably enhanced CO_(2)-to-CO electroreduction performance as high as FE 99.4%,current density 7.2 mA cm^(−2),and TOF 21.17 s^(−1),in a nearneutral aqueous solution at a low overpotential of 525 mV.Density functional theory calculations showed that the prepositioned amino groups,although located not sufficiently close to the active center,serve as hydrogen-bonding donors to stabilize the intermediate Co-CO_(2)adduct and impede the formation of Co-H_(2)O adduct,which not only promotes the CO_(2)reduction reaction but also restrains the hydrogen evolution reaction.
基金supported by the National Natural Science Foundation of China (21731007, 21701191, and 21821003)the Guangdong Pearl River Talents Program (2017BT01C161)the Fundamental Research Funds for the Central Universities (18lgpy42)
文摘Two-dimensional (2D) materials and ultrathin nanosheets have attracted tremendous research interests [1-4]. Exfoliation of porous coordination polymers (PCPs) or metal-organic frameworks (MOFs) with 2D coordination structures is emerging as a viable strategy for preparation of new types of 2D materials [5-8]. The relatively weak bonding within and strong interactions between 2D coordination networks are the main problems for successful exfoliation [9]. Pretreatments of the layered MOFs to expand the interlayer distances can be helpful [10-12]. Capturing the exfoliation intermediates and visualizing their structures are valuable for understanding the exfoliation mechanism and confirming the structures of the final 2D materials [11,12].
基金This work was supported by the NSFC(21731007 and 21821003)the Guangdong Pearl River Talents Program(2017BT01C161).
文摘Understanding,controlling,and utilizing the flexibility of adsorbents are of great importance and difficulty.Analogous with conventional solid materials,downsizing to the nanoscale is emerging as a possible strategy for controlling the flexibility of porous coordination polymers(or metal-organic frameworks).We report a unique flexibility controllable by crystal size at the micrometer to submillimeter scale.Template removal transforms[Cu_(2)(pypz)_(2)]·0.5p-xylene(MAF-36,Hpypz=4-(1H-pyrazol-4-yl)pyridine)with one-dimensional channels toα-[Cu_(2)(pypz)_(2)]with discrete small cavities,and further heating gives a nonporous isomerβ-[Cu_(2)(pypz)_(2)].Both isomers can adsorb p-xylene to give[Cu_(2)(pypz)_(2)]·0.5p-xylene,meaning the coexistence of guest-driven flexibility and shape-memory behavior.The phase transition temperature fromα-[Cu_(2)(pypz)_(2)]toβ-[Cu_(2)(pypz)_(2)]decreased from~270℃ to~150℃ by increasing the crystal size from the micrometer to the submillimeter scale,ca.2-3 orders larger than those of other size-dependent behaviors.Single-crystal X-ray diffraction showed coordination bond reconstitution and chirality inversion mechanisms for the phase transition,which provides a sufficiently high energy barrier to stabilize the metastable phase without the need of downsizing to the nanoscale.By virtue of the crystalline molecular imprinting and gate-opening effects,α-[Cu_(2)(pypz)_(2)]andβ-[Cu_(2)(pypz)_(2)]show unprecedentedly high p-xylene selectivities of 16 and 51,respectively,as well as ultrafast adsorption kinetics(<2 minutes),for xylene isomers.
基金supported by the National Natural Science Foundation of China(21731007,22090061,21821003,22161021)the support of Jiangxi Province(jxsq2018106041)the“Young Elite Scientists Sponsorship Program”by CAST。
文摘Adsorptive separation of p-xylene(pX)from xylene isomers is a key process in chemical industry,but known adsorbents cannot simultaneously achieve high adsorption selectivity,capacity,and rate.Here,we demonstrate gating ultramicropore as a solution for this challenge.Slight modification of the synthetic condition gives rise to isomeric metal-organic frameworksα-[Zn(pba)](MAF-88,H2pba=4-(1H-pyrazol-4-yl)benzoic acid)andβ-[Zn(pba)](MAF-89)possessing similar pillared-column structures,porosities,and high pX capacities of 2.0 mmol g^(−1),but very different framework/pore topologies,pore sizes,and pX selectivities.For binary and ternary mixtures of liquid xylene isomers,MAF-88 with narrow one-dimensional(1D)channels shows pX selectivity of 11 and 1.6,while MAF-89 with 3D-connected quasi-discrete pores shows pX selectivity up to 221 and 46,respectively.Thermogravimetry,differential scanning calorimetry,and time-dependent separation experiments reveal that the kinetic effects of the gating pores play more important roles than the thermodynamic effects,which is further confirmed by single-crystal X-ray diffraction and computational simulations.
基金supported by the NSFC(Nos.21731007,21821003,22090061,and 22071272)the Guangdong Pearl River Talents Program(No.2017BT01C161)the Guangzhou Science and Technology Bureau(No.202102020296).
文摘Solvothermal reactions of 3,6-di(pyridin-4-yl)-9H-carbazole(dpc)with Cu(ll)yielded crystals of two new coordination complexes,namely[Cu(CH_(3)COO)_(2)(dpc)(H_(2)O)_(2)]n-xGuest(1)and[Cu_(13)(HCOO)_(16)(dpc)16(H_(2)O)6](HCOO)10-Guest(2),in which CH_(3)COO_and HCOO-were generated from the hydrolysis of the solvents A/zAZ-dimethylacetamide(DMA)and A/zA/-dimethylformamide(DMF),respectively.Single-crystal X-ray diffraction showed that 1 possesses simple wavy coordination chains,while 2 possesses large molecular bowls/sieves with outer and inner effective sizes of 30.2 × 30.2 × 25.5 A^(3) and 15.0 × 15.0 × 18.6 A^(3),respectively,which consists of 4 linear Cu_(3)(HCOO)_(4)(H_(2)O)clusters and 12 dpc ligands as the square-shaped wall and a claw-like Cu(dpc)_(4) fragment as the bottle.Guest-free 2 can adsorb considerable amounts of CO_(2)/H_(2)O and CH_(3)OH but completely exclude C2H4 and C3H6z which shows a potential application for olefin drying.
基金supported by the National Basic Research Program of China (2014CB845602)the National Natural Science Foundation of China (21225105, 21473260)the Natural Science Foundation of Guangdong (S2012030006240)
文摘Solvothermal reaction of Zn(NO_3)_2, 4-(1H-pyrazol-4-yl)pyridine(Hpypz) and 1,3,5-benzenetricarboxylic acid(H_3btc) in N,N-dimethylacetamide(DMA) produced a new porous coordination polymer [Zn_5(pypz)_4(btc)_2](1). Single-crystal X-ray diffraction study of 1 showed that deprotonated pypz~– ligands served as 1,2,4-triazolate-like ligands, linking Zn(II) ions to form porous two-dimensional(2-D) sql-a layers {Zn(pypz)}^+, which were further connected by eight-legged pillars {Zn_2(btc)_4(H_2O)_2}^(8–) based on the typical paddlewheel dinuclear Zn_2(RCOO)_4(H_2O)_2 cluster to form a novel type of non-interpenetrated pillared-layer framework with 3-D intersecting pore system and large pore volume. Gas sorption measurements revealed that 1 possesses large BET surface area of 2061 m^2 g^(–1) and very high methane total uptake of 245 cm^3(STP) cm^(–3) at 298 K and 65 bar.
基金supported by the National Natural Science Foundation of China (91622109, 21731007, 21821003)Guangdong Pearl River Talents Program (2017BT01C161)
文摘Hydrophobic ethyl, butyl or hexyl groups were introduced into the dicarboxylate ligand in the fluorescent porous coordination framework [Zn_2(fda)_2(bpy)](LMOF-202, H_2fda=9H-fluorene-2,7-dicarboxylic acid, bpy=4,4′-bipyridine) for improving water stability and tuning oxygen sensitivity. The long hexyl groups gave satisfactory water stability but its oxygen sensitivity is low(70.8% fluorescence quenched at 1 bar O_2(1 bar=105 Pa)). In contrast, the shorter side groups gave high oxygen sensitivity(93.9% fluorescence quenched at 1 bar O_2) and low water stability. The derivation of the Stern-Volmer curves of the O_2 luminescence quenching data from the linear form can be used for detecting trace impurities in the luminescent framework, being much more sensitive than conventional methods such as powder X-ray diffraction. Mixing the ethyl and hexyl groups in the solid-solution manner brought high oxygen sensitivity(96.4% fluorescence quenched at 1 bar O_2) and high water stability simultaneously in the same coordination framework.
基金supported by NSFC(nos.21731007,22090061,21821003,and 22071272)the Guangdong Pearl River Talents Program(no.2017BT01C161).The。
文摘Controlling interpenetration and flexibility behaviors is intriguing and fundamental for porous coordination polymers.We report exceptional interpenetration behaviors involving controllable partial order–disorder structural transformations.A new bis-benzotriazolate ligand(NaH2sbbta)with a twisted and anionic backbone was designed and synthesized.The solvothermal reaction of ZnCl_(2) and NaH_(2)sbbta yielded(Et_(2)NH_(2))_(3)[Zn_(5)Cl_(4)(sbbta)_(3)]·6DEF(2)possessing two-fold interpenetrated anionic pcu networks with symmetry,shape,and charge different from the known analogues.More interestingly,powder and single-crystal X-ray diffractions showed that 2 can undergo solvent-induced structural transformation to form a noninterpenetrated anionic pcu network with larger pores(1).Consequently,1/2 can selectively adsorb/exchange cationic dyes fromneutral and anionic dyes with tunable size selectivity.However,since the transformations are reversible without obvious change of crystal sizes,the network that disappeared in X-ray crystallography should be mainly disordered rather than decomposed.Further,the structural transformations can be suppressed by thermal decomposition/removal of Et_(2)NH_(2)^(+)/Et_(2)NH.Computational simulations indicate that the ordered and disordered structures are stabilized by relatively large and small solvent molecules,respectively.
基金supported by the National Natural Science Foundation of China(22090061,22231012,21821003,22071272)。
文摘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.