Self-assembly of a mixed-ligand metal-coordination polymeric network of cadmium(II) croconate with 4,4'-bipyridine

A new cadmium croconate (C5O5(2-)) complex, [Cd2(C5O5)2(4,4'-bpy)(H2O)]infinity (4,4-bpy=4,4'-bipyridine) with an extended network has been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction studies. The title compound crystallizes in the monoclinic system, space group P2(1)/n, with empirical formula C20H12Cd2N2O12, a=15.9623(3) A, b=7.5837(1) A, c=18.1181(3) A, beta=99.95(2) degrees, and Z=4. Structural determination reveals that the title compound has a bilayered network, containing two crystallographically independent Cd(II) ions in different coordination environments. Cd(1) lies in a distorted pentagonal bipyramidal environment, consisting of three croconate ions and one 4,4'-bpy nitrogen donor, while Cd(2) lies in a distorted octahedral environment, consisting of two croconate anions, one 4,4'-bpy nitrogen donor, and one water molecule. Of the two crystallographic independent croconate ligands, one presents a bis-bidentate adjacent mu3-coordination mode and the other a new bidentate/three-adjacent mu5-coordination mode. A two-dimensional hybrid layer is formed by two rectangular boxes as the building units through the connectivity between Cd(II) and croconate and 4,4'-bpy ligands.     

Cd3(H2O)3((O3PCH2)2NH-CH2C6H4-COOH)2].11H2O: a layered cadmium phosphonate with reversible dehydration/hydration properties

In a recent systematic study on the influence of the reaction temperature on the structure formation in the system CdCl2/H(HO3PCH2)2NH-CH2C6H4-COOH (H5L) /NaOH, [Cd3(H2O)3((O3PCH2)2NH-CH2C6H4-COOH)2].11H2O was obtained as a microcrystalline compound. We have now been able to elucidate the structure from single-crystal data: triclinic, P; a=5.4503(9), b=12.880(2), and c=16.417(3) A; alpha=67.841(6) degrees, beta=80.633(6) degrees, gamma=87.688(8) degrees, V=1052.9(3) A3; Z=1; R1=0.1143, R2=0.2108 (all data); 0.0705, 0.1823 ((I>2sigmaI)). The structure of [Cd3(H2O)3((O3PCH2)2NH-CH2C6H4-COOH)2].11H2O is built up of cadmium phosphonate layers connected by water-mediated hydrogen bonds between aryl-carboxylic acid groups and water molecules coordinated to Cd2+ ions of adjacent layers (C-OH...H2O...H2O-Cd2+). The title compound was characterized by IR spectroscopy and energy dispersive X-ray, elemental, and thermogravimetric analyses. Furthermore, temperature-dependent X-ray diffraction data are presented. [Cd3(H2O)3((O3PCH2)2NH-CH2C6H4-COOH)2].11H2O can be reversibly dehydrated, and mechanical stress and grinding in the presence of water leads to the intercalation of additional water molecules.     

Novel eclipsed 2D cadmium(II) coordination polymers with open-channel structure constructed from terephthalate and 3-(2-pyridyl)pyrazole: crystal structures, emission properties, and inclusion of guest molecules

Five new eclipsed two-dimensional (2D) coordination polymers, [[Cd(2)(TPT)(2)L(2)](GM(1))(3/2)(H(2)O)](infinity) (1) (TPT = terephthalate, L = 3-(2-pyridyl)pyrazole, GM(1) = terephthalic acid), [[Cd(TPT)L](GM(2))(H(2)O)(2)]( infinity) (2) (GM(2) = L = 3-(2-pyridyl)pyrazole), [[Cd(TPT)L](GM(3))(1/2)(H(2)O)](infinity) (3) (GM(3) = mesitylene), [[Cd(4)(TPT)(4)L(4)](GM(4))(7/2)](infinity) (4) (GM(4) = tetramethylbenzene), and [[Cd(TPT)L](GM(5))(1/2)](infinity) (5) (GM(5) = naphthalene), have been synthesized and characterized by X-ray diffraction. All the five complexes take the similar eclipsed 2D open-channel framework with different guest molecules included in the cavities of their channels. TGA analysis indicates that the eclipsed open-channel frameworks are thermally stable up to 300 degrees C. The porous property of the 2D framework of 5 was also investigated by the XRPD technique, which indicated that the guest molecules included in the open-channel frameworks are removable and the framework is maintained after the removal of the guest molecules. Moreover, complexes 1-5 also display strong blue emission in the solid state.     

Selective CO2 adsorption in a robust and water-stable porous coordination polymer with new network topology

A robust and water-stable porous coordination polymer [Cd(NDC)(0.5)(PCA)]·G(x) (1) (H(2)NDC = 2,6-napthalenedicarboxylic acid, HPCA = 4-pyridinecarboxylic acid, G = guest molecules) with new network topology has been synthesized solvothermally. The framework is 3D porous material and forms a 1D channel along the c-axis, with the channel dimensions ~9.48 × 7.83 ?(2). The compound has high selectivity in uptake of CO(2) over other gases (H(2), O(2), Ar, N(2), and CH(4)). The framework is highly stable in presence of water vapor even at 60 °C. The high CO(2) selectivity over other gases and water stability makes the compound promising candidate for industrial postcombustion gas separation application.     

Pillared, 3D metal-organic frameworks with rectangular channels. Synthesis and characterization of coordination polymers based on tricadmium carboxylates

Hydro(solvo)thermal reactions between cadmium(II) perchlorate and 4-pyridinecarboxaldehyde in the presence of various guest molecules have resulted in a series of 3-D coordination polymers based on tricadmium carboxylates [Cd6(isonicotinate)10(H2O)2](ClO4)2(EtOH)4(H2O)4, 1, [Cd3(isonicotinate)5 (EtOH)](ClO4)(EtOH)(4-nitroaniline)0.5, 2, and [Cd6(isonicotinate)11](ClO4)(EtOH)2(H2O)2(4-cyanopyridine)0.5, 3. X-ray single crystal structure determinations show that they exhibit similar pillared, 3D framework structures based on tricadmium carboxylate building blocks. Rectangular channels are clearly present in these polymeric networks and are occupied by perchlorate anions and disordered guest molecules. Quantitative NMR and X-ray powder diffraction studies and thermogravimetric analyses (TGA) reveal that these coordination networks are capable of accommodating different guest molecules. More significantly, the guest molecules can be readily removed via evacuation to result in nanoporous polymeric coordination networks retaining the framework structures of the pristine solids. Crystal data for 1: monoclinic space group P2(1)/n, a = 19.041(1) A, b = 23.654(1) A, c = 21.568(1) A, beta = 95.440(1) degrees, and Z = 4. Crystal data for 2: triclinic space group P1, a = 12.050(1) A, b = 12.277(1) A, c = 19.103(1) A, alpha = 91.669(1) degrees, beta = 96.850(1) degrees, gamma = 117.945(1) degrees, and Z = 2. Crystal data for 3: monoclinic space group P2(1)/n, a = 19.038(1) A, b = 23.834(1) A, c = 21.756(1) A, beta = 97.580(1) degrees, and Z = 4.     

A New Cadmium（Ⅱ） Coordination Polymer Incorporating a 3D Framework with 1D Channels Bridged by Flexible Cyclohexane-1,2,4,5-tetracarboxylate Ligand

The hydrothermal reaction of Cd(OAc)2·2H2O, 4,4'-bpy and cyclohexane-1,2,4,5-tetracarboxylic acid (H4L) yields a three-dimensional (3D) coordination porous framework [Cd2LI(4,4'-bpy)1.5(H2O)2]n·2nH2O, which was characterized by single-crystal X-ray diffraction (MoKα radiation, λ = 0.71073), elemental analysis and IR. This complex crystallizes in the monoclinic system, space group C2/c with a = 25.951(3), b = 11.6618(12), c = 20.046(2) , β = 114.863(2)o, V = 5504.4(10) 3, Z = 8, Dc = 1.900 g/cm3, Mr = 787.30, μ = 1.615 mm-1, F(000) = 3128, the final R = 0.0978 and wR = 0.1780. The structure of the complex is a 3D coordination Cd-carboxylate framework consisting of 1D hexagonal channels along the c-axis filled with the bridging 4,4'-bpy ligands. The 4,4'-bpy ligands with two kinds of conformations are located alternately in the channels through coordination and hydrogen interactions to support the whole porous framework, in which the conformation-flexible cyclohexane-1,2,4,5-tetracarboxylate ligand adopts the I (e,a,a,e) conformation and acts as a pentadentate ligand to connect five Cd(Ⅱ) atoms via the carboxylate groups in different coordination modes.     

Crystal structure and characterization of the dinuclear Cd(II) complex [Cd(H2O)2(o-HOC6H4COO)2]2

The structure of a new binuclear cadmium (II) complex, [Cd(H2O)2(Sal)2]2 (Sal= salicylate), has been determined by X-ray crystallography. It was also characterized by elemental analysis, its IR spectrum and thermogravimetric-differential scanning calorimetry (TG-DSC). It crystallizes in the monoclinic system, space group P2(1)/c, with lattice parameters a = 15.742(3) A, b = 12.451(3) A, c = 7.7225(15) A, beta = 96.07(3)degrees and Z = 4. Two cadmium (II) ions are bridged by two mu(2)-carboxy oxygen atoms. Each cadmium atom lies in a distorted capped octahedron coordination geometry. The thermal gravimetry (TG) data indicate that there are four discrete decomposition steps with two endothermic peaks and one exothermic peak. The final thermal decomposition product is CdO.     

Hydrothermal Synthesis and Crystal Structure of a Cd~(2+) Supramolecular Coordination Complex{[Cd_2(HCAM)_2(H_2O)_4]·3.5H_2O}_n with a 3D Metal-organic Open Framework

<正>A three-dimensional coordination polymer {[Cd_2(HCAM)_2(H_2O)_4]·3.5H_2O}_n was synthesized by the hydrothermal reaction of H_3CAM(H_3CAM=4-hydroxypyridine-2,6-dicerboxylic acid)and Cd(NO_3)_2·4H_2O.The structure was characterized by elemental analysis,thermal gravimetric analysis,infrared spectroscopy and single-crystal X-ray diffraction.It crystallizes in triclinic,space group P_1~-with a= 9.4389(19),b=11.009(2),c=11.192(2)(?),α=87.87(3),β= 74.63(3),γ=81.22(3)°,V=1108.2(4)(?)~3,Z=2,D_c=2.164g/cm~3,μ=2.011 mm~(-1),F(000)=710,R =0.0419 and wR=0.1170.X-ray analysis reveals that the title compound adopts a one-dimensional staircase structure by carboxyl of H_3CAM and water molecules,and it is further linked by hydrogen bonds to form a 3-D metal-organic open framework.The thermal gravimetric analysis displays that the framework exists stably below 300℃.     

Three-dimensional porous coordination polymer functionalized with amide groups based on tridentate ligand: selective sorption and catalysis

To create a functionalized porous compound, amide group is used in porous framework to produce attractive interactions with guest molecules. To avoid hydrogen-bond formation between these amide groups our strategy was to build a three-dimensional (3D) coordination network using a tridentate amide ligand as the three-connector part. From Cd(NO3)2.4H2O and a three-connector ligand with amide groups a 3D porous coordination polymer (PCP) based on octahedral Cd(II) centers, {[Cd(4-btapa)2(NO3)2].6H2O.2DMF}n (1a), was obtained (4-btapa = 1,3,5-benzene tricarboxylic acid tris[N-(4-pyridyl)amide]). The amide groups, which act as guest interaction sites, occur on the surfaces of channels with dimensions of 4.7 x 7.3 A2. X-ray powder diffraction measurements showed that the desolvated compound (1b) selectively includes guests with a concurrent flexible structural (amorphous-to-crystalline) transformation. The highly ordered amide groups in the channels play an important role in the interaction with the guest molecules, which was confirmed by thermogravimetric analysis, adsorption/desorption measurements, and X-ray crystallography. We also performed a Knoevenagel condensation reaction catalyzed by 1a to demonstrate its selective heterogeneous base catalytic properties, which depend on the sizes of the reactants. The solid catalyst 1a maintains its crystalline framework after the reaction and is easily recycled.     

Synthesis and characterization of a porous magnetic diamond framework, Co3(HCOO)6, and its N2 sorption characteristic

[Co3(HCOO)6](CH3OH)(H2O) (1), the isostructural analogue of the porous magnet of coordination framework [Mn3(HCOO)6](CH3OH)(H2O), and its desolvated form [Co3(HCOO)6] (2) were prepared and characterized by X-ray and neutron diffraction methods, IR, thermal analyses, and BET, and their magnetic properties were measured. The parent compound, 1, crystallizes in the monoclinic system, space group P21/c, a = 11.254(2) A, b = 9.832(1) A, c = 18.108(3) A, beta = 127.222(2) degrees , V = 1595.5(4) A3, Z = 4, R1 = 0.0329 at 180 K. It possesses a unit cell volume that is 9% smaller than [Mn3(HCOO)6](CH3OH)(H2O) due to the smaller radius of Co2+ ion. Compared with the parent compound 1, the desolvated compound 2 has slightly larger lattice with cell parameters of a = 11.2858(4) A, b = 9.8690(4) A, c = 18.1797(6) A, beta = 127.193(2) degrees , V = 1613.0(1) A3, R1 = 0.0356 at 180 K. The cell parameters of 2, obtained from neutron powder data at 2 K, are a = 11.309(2) A, b = 9.869(1) A, c = 18.201(3) A, beta = 127.244(8) degrees , V = 1617.3(5) A3. The pore volume reduces from 33% to 30% by replacing Mn by Co. The material exhibits a diamond framework based on Co-centered CoCo4 tetrahedral nodes, in which all metal ions have octahedral coordination geometry and all HCOO groups link the metal ions in syn-syn/anti modes. It displays thermal stability up to 270 degrees C. The compound easily loses guest molecules without loss of crystallinity, and it partly reabsorbs water from the atmosphere. Significant N2 sorption was observed for the desolvated framework suggesting that the material possesses permanent porosity. The magnetic properties show a tendency to a 3D long-range magnetic ordering, probably antiferromagnetic with a spin canting arrangement below 2 K.     

A Novel （3,4）-Connected Self-penetrating Net, [Cd_3（OABDC）_2（bipy）_2（H_2O）_2]_n

A new luminescent Cd(Ⅱ) compound, [Cd3(OABDC)2(bipy)2(H2O)2]n (1, H3OABDC = 5-oxyacetateisophthalic acid, bipy = 4,4'-bipyridine), has been prepared by the assembly of Cd(Ⅱ) salt with the mixed ligands of H3OABDC and 4,4'-bipy under hydrothermal conditions. The crystal structure is of monoclinic, space group P2/n with a = 13.6730(5), b = 10.1265(3), c = 15.9752(4) , β = 103.061(3)o, V = 2154.70(11) 3, C40H34Cd3N4O18, Mr = 1195.94, Z = 2, Dc = 1.843 g/cm3, F(000) = 1180, μ = 1.549 mm-1, the final R = 0.0409 and wR = 0.1291 for 2746 observed reflections (I > 2σ(I)). Single-crystal X-ray structural analysis reveals that compound 1 features a self-penetrating two-dimensional (2D) layered structure. According to topology analysis, this 2D framework can be characterized as a (3,4)-connected (6.72)2 (62.8)2 (73.8.102) net that has never been reported before. Finally, these 2D layers are further linked by intermolecular hydrogen bonds and π…π interactions to form a three-dimensional (3D) supramolecular framework. Moreover, Compound 1 exhibits strong blue photoluminescence at room temperature.     

三维金属有机骨架微孔晶体化合物Cd5(BTC)4(H2O)8·6H2O的合成与晶体结构

通过改变合成条件合成了最大宽度达到2.6 nm的特殊“Z”字形孔道的新型金属有机骨架微孔晶体化合物Cd5(BTC)4(H2O)8·6H2O, 并通过ICP、元素分析、热重(TGA)和X射线单晶衍射分析对其进行了表征.     

Hydrothermal syntheses and crystal structures of complex-linked three-Dimensional coordination vanadium selenites: M(4,4'-bipy)(H(2)O)V(2)Se(2)O(10) (M = Co,Ni)

Two inorganic-organic hybrid compounds with the formula M(4,4'-bipy)(H(2)O)V(2)Se(2)O(10) (M = Co, Ni) were hydrothermally synthesized and characterized by single-crystal X-ray diffraction. Compounds Co(4,4'-bipy)(H(2)O)V(2)Se(2)O(10) (1) and Ni(4,4'-bipy)(H(2)O)V(2)Se(2)O(10) (2), which are structural analogues, crystallize in the triclinic space group Ponemacr; with crystal data a = 7.9665(3) A, b = 8.1974(3) A, c = 13.8096(4) A, alpha = 85.704(2) degrees, beta = 73.5180(10) degrees, gamma = 75.645(2) degrees, V = 837.76(5) A(3), and Z = 2 and a = 7.9489(19) A, b = 8.128(2) A, c = 13.709 A, alpha = 85.838(6) degrees, beta = 73.736(8) degrees, gamma = 75.594(9) degrees, V = 823.5(4) A(3), and Z = 2, respectively. [M(4,4'-bipy)(H(2)O)V(2)Se(2)O(10)] (M = Co, Ni) have a three-dimensional structure and consist of two subunits, [(VO(2))(SeO(3))](-) infinite chains and [M(4,4'-bipy)(H(2)O)](2+) fragments. The [(VO(2))(SeO(3))](-) chains are composed of [V(2)Se(4)O(14)](4)(-) clusters linked by VO(4)N triangular bipyramids. The 4,4'-bipy molecule as a bifunctional organic ligand is directly linked to Co or Ni and V atoms, affording the three-dimensionality. The compounds were characterized by infrared spectroscopy and differential thermal and thermogravimetric analyses.     

三维无机-有机杂化骨架微孔材料Cd(HBTC)(EG)·8(H2O)的合成与结构

由于无机-有机杂化微孔晶体材料在选择性催化、分子识别和可逆性主客体分子(离子)交换等方面存在潜在的应用前景,已经越来越引起人们的广泛注意.传统的沸石和分子筛微孔晶体材料以硅酸盐、硅铝酸盐、磷铝酸盐和无机金属磷酸盐为骨架,新型的无机-有机杂化微孔晶体材料用刚性和热稳定性较好的有机分子和金属离子作为结构单元.均苯三甲酸(H3BTC)是常用的含氧有机配.     

A homochiral luminescent 2D porous coordination polymer with collagen-type triple helices showing selective guest inclusion

A homochiral luminescent porous coordination polymer, [Cd(L)(H(2)O)]·3H(2)O, with interconnected collagen like triple-helical chains has been synthesized solvothermally by using cadmium(II) salt and a newly designed d-isosorbide-based, enantiomerically pure chiral ligand. The framework is a 2D porous material and forms a 1D channel along the a axis, with the channel dimensions ~6.2 × 4.4 ?(2). The compound has high selectivity in the uptake of water and methanol over other solvents (e.g., tetrahydrofuran, ethanol, benzene, and cyclohexane) inside the channels.     

Synthesis, Characterization and Crystal Structure of an Inorganic-organic Composite Metatungstate: [Co(4,4''-bipy)2(H2O)4](4,4''-H2bipy)2[H2W12O40]·5.5H2O

A novel hybrid compound [Co(4,4'-bipy)2(H2O)4](4,4'- H2bipy)2[H2W12O40]·5.5H2Ohas been synthesized from an acidified aqueous solution and characterized by elemental and thermal analyses, IR and UV spectroscopy, and single-crystal X-ray structure determination. Structure analysis indicates that the title compound is of monoclinic, space group C2/c, with a = 21.315(9), b = 15.303 (7), c = 24.139(10) (A), β = 105.170(5)o, V = 7599(6) (A)3, Mr = 3706.99, Z = 4, F(000) = 6616, Dc = 3.231, μ = 18.395 mm-1, R = 0.0652 and wR = 0.1594. X-ray crystallographic study shows that the title compound consists of one [Co(4,4'-bipy)2(H2O)4]2 cation, two diprotonated 4,4'-bipyridine molecules, 5.5 water molecules of crystallization, and one metatungstate polyoxoanion [H2W12O40]6-, which approaches an effective Td point symmetry. TG-DTA analysis indicates that the framework of the metatungstate polyoxoanion is collapsed at 587.0 ℃.     

Supramolecular isomers in the same crystal: a new type of entanglement involving ribbons of rings and 2D (4,4) networks polycatenated in a 3D architecture

The reaction of corresponding cadmium salts with the flexible ligand 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene (bbtz) affords the 3D coordination network [Cd3(bbtz)6(H2O)6](BF4)(6.1.75H2O (1), containing ribbons of rings and planar 2D (4,4) networks polycatenated with each other, the undulating 2D (4,4) network [Cd(bbtz)2(H2O)2](ClO4)2.2H2O (2), and ribbons of rings [Cd(bbtz)2(H2O)2](BF4)2.3DMF (3) and [Cd(bbtz)2(H2O)2](ClO4)2.3DMF (4).     

Synthesis,Crystal Structure and Antitumor Activity of a New Coordination Polymer [Cd（C（14）H（10）N3O5）2（C5H5N）2]n

A new cadmium coordination polymer,[Cd(C14H10N3O5)2(C5H5N)2]n,has been synthesized by the reaction of 2-hydroxy-N'-(4-nitrobenzoyl)benzohydraizide with cadmium acetate in pyridine and ethanol mixture solution.Its molecular structure was characterized by elemental analysis,IR spectra and X-ray crystal structure determination.Crystal data for this compound:tetragonal,space group I41/a,Mr=871.10,a=16.960(6),b=16.960(6),c=28.612(6) ,V= 8230(4)3,Z=8,Dc=1.406 g·m-3 and F(000)=3536.the final R=0.0326,wR=0.0847 for 2682 observed reflections with I 2σ(I) and R=0.0460,wR=0.0896 for all reflections.In the molecular structure of the complex,the cadmium atoms are coordinated to four N and two O atoms forming a slightly distorted octahedral geometry.The intermolecular hydrogen bonds link the neighboring molecules to form a coordination polymer which was then evaluated for its anti-tumor activities against two kinds of cell lines (K562 and BGC) by MTT method.A preliminary bioactivity study indicates that the complex has distinct inhibitory effect on K562 cell lines.     

Reversible transformation of ZnII coordination geometry in a single crystal of porous metal-organic framework [Zn3(ntb)2(EtOH)2].4 EtOH

A 3D porous metal-organic framework [Zn3(ntb)2(EtOH)2]n.4nEtOH (1) that generates 1D channels of honeycomb aperture has been prepared by the solvothermal reaction of Zn(NO3)(2).6 H2O and 4,4',4'-nitrilotrisbenzoic acid (H3NTB) in EtOH at 110 degrees C. Framework 1 exhibits reversible single-crystal-to-single-crystal transformations upon removal and rebinding of the coordinating EtOH as well as the EtOH guest molecules, which give rise to desolvated crystal [Zn3(ntb)2]n (1') and resolvated crystal [Zn3(ntb)2-(EtOH)2]n.4nEtOH (1'). The X-ray structures indicate that 3D host framework is retained during the transformations from 1 to 1' and from 1' to 1', but the coordination geometry of ZnII ions changes from/to trigonal bipyramid to/from tetrahedron, concomitant with the rotational rearrangement of a carboxylate plane of the NTB3- relative to its associated phenyl ring. To retain the single crystal integrity, extensive cooperative motions must exist between the molecular components throughout the crystal. Framework 1' exhibits permanent porosity, thermal stability up to 400 degrees C, and blue luminescence, and high storage capabilities for N2, H2, CO2, and CH4.     

A Dynamic Crystal‐to‐Amorphous Transformation Microporous ZnII Mixed Neutral‐ligand Metal‐organic Polymer {[Zn(bpp)2(μ‐4,4′‐bipy)(H2O)2](ClO4)2·H2O}n

A new rarely reported Zn^II mixed‐polypyridine coordination polymer with both rigid and flexible spacers, {[Zn(bpp)₂(μ‐4,4′‐bipy)(H₂O)₂](ClO₄)₂ · H₂O}_n ( 1 ), has been synthesized and characterized by elemental analysis, IR‐, ¹H NMR‐, ¹³C NMR spectroscopy and single‐crystal X‐ray diffraction. The thermal stability of compound 1 was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The single‐crystal X‐ray structure of 1 shows that the complex has been formed from a 1D polymer as a result of bridging by the 4,4′‐bipy ligands. Solution and solid‐state luminescent spectra of the compound 1 indicate intense fluorescent emissions at ca. 353.6 and 468.8 nm, respectively. Removal of the interstitial water guest molecules results in a loss of crystallinity, but exposure to water vapor reestablishes the original structure, thus constituting 1 as a third‐generation porous framework.