Topology and porosity control of metal–organic frameworks through linker functionalization

Topology and porosity control of Zr6-based MOFs was achieved by introducing steric functionalization into the conformations of substituted tetracarboxylate linkers.

S-1  Tables   Table S1. Summary of the crystal data and structure refinement details for NU-1008 Table S3 The bending angle between center benzene plane and peripheral arms benzene (ψ), the dihedral angles of the arm benzene to the center benzene (ϕ) and those of the carboxylate to the arm benzene (δ), angles between arm benzenes (α/α') and the angle of nitro group to center benzene (γ) measured from single crystal structures of three

Section 2 Ligands Synthesis
Synthesis of 1,2,4,5-tetrakis(4-carboxyphenyl)benzene (L1) 1 (a) 100 mL of p-tolylmagnesium bromide (1 M in THF, 100 mmol) was added under nitrogen to a flask containing 5 g of hexabromobenzene (9.07 mmol). The mixture was stirred at room temperature for 15 h. The reaction was poured on ice then 50 mL of 6 M HCl was added. The mixture was extracted with THF (3 x 200 mL). The organics were combined and the solvent was removed via rotary evaporation. The solid was then washed with hexanes and cold acetone. Isolated yield: 2.75g, 70% based on hexabromobenzene. (b) An amount of 2 g from (a) was placed in a 100 mL teflon lined vessel. An amount of 24 mL of water and 6 mL of HNO 3 were then added. The vessel was sealed and heated at 180 °C for 24 h. The resulting solid was collected by filtration and washed with THF/CHCl 3 (7:3). Isolated yield: 1.85g, 75%. Synthesis of 1,2,4,5-tetrakis(4-carboxyphenyl-3-nitrobenzene (L2) 2 (a) A mixture of 1,2,4,5-tetrabromobenzene (3.7 g), NaNO 3 (1.8 g), and conc. H 2 SO 4 (10 mL) was heated on a water bath with stirring for 7 h. The reaction mixture was cooled, poured onto ice, and neutralized with NaOH. The precipitate that formed was filtered off, washed with water, dried, and recrystallized from benzene. (b) To a 500 mL round bottom flask, (a) (4.39 g), 4-ethoxycarbonylphenylboronic acid (23.28 g), potassium carbonate (16.6 g), 210 mL toluene, 21 mL ethanol and 21 mL water were added. The mixture was purged with nitrogen for 30 min then palladium tetraphenylphosphine (800 mg) was added into the mixture. The mixture was further purged with nitrogen for another 15 min, then heated at 110 °C for 65 h. After the reaction was done, the solid impurity was filtered off and the filtrate was evacuated under vacuum. The rough product was extracted with dichloromethane and water. The organic layer was evacuated and the obtained solid was washed with methanol to get pure product. Isolated yield: 4.59g, 64%. (c) 1 g (b) was added into a mixture of 30 mL THF, 30 mL methanol and 23 mL 10 M NaOH solution. The mixture was refluxed overnight to be completely hydrolyzed. Concentrated hydrogen chloride was slowly added into the reaction (dropwise) with stirring through an addition funnel until the solution had reached a pH of 1. The formed white precipitate was collected, washed with water and dried. Isolated yield: 600 mg, 71%.

Synthesis of 1,2,4,5-tetrakis(4-carboxyphenyl)-3,6-dibromobenzene (L3) 3
(a) 100 mL of p-tolylmagnesium bromide (1 M in THF, 100 mmol) was added under nitrogen to a flask containing 5g of hexabromobenzene (9.07 mmol). The mixture was stirred at room temperature for 15 h (gray suspension). The reaction was placed on an ice-bath. A mixture of 7 mL of bromine and 60 mL of CCl 4 were placed in an addition funnel and then added drop wise to the reaction mixture. The reaction was stirred at room temperature for 1.5 h and then poured on ice, which was followed by the addition of 50 mL of 6 M HCl. The solid was filtered and washed with methanol. Isolated yield: 2.25 g, 42 %. (b) An amount of 2 g from (a) was placed in a 100 mL teflon lined vessel. An amount of 24 mL of water and 6 mL of HNO 3 were then added. The vessel was sealed and heated at 180 °C for 24 h. The resulting solid was collected by filtration and washed S-6 with THF/CHCl 3 (7:3). Isolated yield: 1.85g, 75%.

Section 4 Material Characterization
X-ray Diffraction Analyses. Powder x-ray diffraction (PXRD) patterns were recorded on a Rigaku X-ray Diffractometer Model SmartLab equipped with an 18 kW Cu rotating anode, an MLO monochromator, and a high-count-rate scintillation detector. Measurements were made over the range 1 °<2θ< 30 ° in 0.05 ° step width with a 5 °/min scanning speed. N 2 Sorption Measurements. N 2 adsorption and desorption isotherms on activated materials were measured on a Micromeritics ASAP 2020 (Micromeritics, Norcross, GA) instrument at 77 K. Around 30 mg of sample was used in each measurement and the specific surface areas were determined using the Brunauer−Emmett−Teller model from the N 2 sorption data in the region P/P 0 = 0.005-0.05. Pore size distributions were obtained using DFT calculations using a carbon slit-pore model with a N 2 kernel. Proton NMR. MOF samples (1 mg) were digested with NaOD solution (0.1 M in deuterium oxide, 150 μL). After sonication for 20 min, another 500 μL of deuterium oxide was added into the mixture to dilute the solution. Proton NMR spectra were collected on a Bruker Avance III 500 MHz system equipped with DCH CryoProbeand automated with a BACS-60 autosampler.

Diffuse Reflectance for Infrared Fourier Transform Spectroscopy (DRIFTS).
DRIFTS spectra were recorded on a Nicolet 6700 FTIR spectrometer equipped with an MCT detector. The detector was cooled with liquid N 2 and the spectra were collected under Ar atmosphere. KBr was utilized as a background spectrum. Thermogravimetric Analyses (TGA). TGA was performed on a TGA/DCS 1 system (Mettler-Toledo AG, Schwerzenbach, Switzerland), which runs on a PC with STARe software. Samples were heated from 25 to 900 °C at a rate of 10 °C/min under air with flow rate 20 mL/min. CO 2 Sorption Measurement. CO 2 adsorption and desorption isotherms on activated materials were measured on a Micromeritics ASAP 2020 (Micromeritics, Norcross, GA) instrument at 298 K in water bath. Stability under Acidic Condition. The stability of materials was tested by soaking the materials in 0.5 M HCl aqueous solution for 10 h. The crystallinity of materials was characterized by X-ray diffraction analyses after decanting the soaking solution. S-17

Section 5 Single-crystal X-ray Diffraction Analyses
Single crystals of NU-1008 and NU-904 were mounted on MicroMesh (MiTeGen) with paraton oil. The data was collected on a 'Bruker APEX-II CCD' diffractometer with a Mo or Cu Kα microfocus X-ray source. The crystals were kept at the desired temperatures during data collection. Using Olex2 2 (for NU-1008) or Yadokari-XG (for NU-904) softwares 4 , the structure was solved with the ShelXT 3 structure solution program using Intrinsic Phasing and refined with the ShelXL 4 refinement package using Least Squares minimization. The disordered non-coordinated solvents were removed using the PLATON SQUEEZE program. The refinement results are summarized in Table S1.

Refinement Detail of NU-904
We firstly attempted to solve the structure with the hexagonal cell, which indicated Zr 18 clustered MOF structure. However, the least-squares refinement of the crystal structure did not converge. As similar to the previous case of PCN-223 5 , the data should be interpreted as the twinning with reticular merohedry 6 , and the observed Zr 18 cluster can be refined as three overlaps of Zr 6 cluster with different orientation (Fig. S14). Because the coordinating OH/OH 2 groups pointing along c-axis were clearly observed, we interpreted the structure as the 8-connected Zr 6 cluster MOF structure, instead of 12connected cluster MOF structure. By lowering the symmetry to monoclinic P and using PART command (PART 1, 2, 3), the twinning structures was successfully divided into 3 components with the same occupancies (1/3). Some structural and thermal parameter restraints (DFIX, DANG, SADI, FLAT, RIGU, SIMU, ISOR) were used in the refinements. And one thermal parameter constraint (EADP) on bridged oxygens (O2X, O2Y, O2Z) on Zr 6 node was also used in the refinement. S-20

Section 6 CO 2 Insertion Reaction
Batch reactions were carried out by using NU-903, NU-1008 and NU-904 as catalysts for CO 2 insertion into styrene oxide. The styrene oxide (0.2 mmol), tetrabutylammonium bromide (6.5 mg, 0.02 mmol) pre-dissolved in 400 μL of acetonitrile and MOF material (4.0 mol %) were added to an autoclave reactor, which had previously been dried for 6 h at 80 °C. The autoclave reactor was evacuated, purged with CO 2 , and then placed under a constant pressure of CO 2 under 5 atm for 15 min to allow the system to equilibrate. Then the pressure was reduced to 1 atm of gauge pressure and the reaction was carried out at room temperature for 24 h. At the end of the reaction, the reactor was placed in an ice bath for 10 min and then opened. After catalyst separation by centrifugation, a small aliquot of the supernatant reaction mixture was taken to be analyzed by 1 H NMR to calculate the conversion of the reaction.   Table S3 The bending angle between center benzene plane and peripheral arms benzene (ψ), the dihedral angles of the arm benzene to the center benzene (ϕ) and those of the carboxylate to the arm benzene (δ), angles between arm benzenes (α/α') and the angle of nitro group to center benzene (γ) measured from single crystal structures of three