Preparation Of Hydrogen-Bonded Supramolecular Metal-Organic Frameworks For Gas Adsorption

Hydrogen-bonded organic frameworks(HOFs)are an emerging class of porous materials,which are assembled with hydrogen bonding interactions.HOFs have a lot of advantages,such as high crystallinety,mild synthesises condition,easy purification and regeneration by simply recrystallization etc.However,the flexible and weak of hydrogen bonds usually makes the HOFs rather fragile and diffcult to matian the permanent porosity,which greatly hampers the development and adsorption sparations application of HOFs.In this work,a series of supramolecular metal-organic framework(SMOFs)have been designed and synthesized by introducing the metal and subsitituting the anion based on the HOFs,and the adsorption separation behavous of SMOFs for light hydrocarbon have been investigated.In addition,the other synthetic method,post-synthesised anion exchange,has been established to prepare the SMOF,which offering a new clue for novel SMOFs.For the first time to sythesize and report a SMOF material,SMOF-GeFSIX-1,which were characterized using SXRD,PXRD and TGA to analyze the property and strucure.The results revealed that SMOF-GeFSIX-1 was successfully synthesized by slow diffusion with the one-dimension pore apeture of 3.5 A×3.5A in diameter,which is isostructure with the previously reported material SMOF-SIFSIX-1.And the adsorption isotherm shows that SMOF-GeFSIX-1 have established the permanenty porosity and 264.0 m2/g of the BET surface area.More interestingly,SMOF-GeFSIX-1 could be irreversibly transformed into SMOF-SIFSIX-1 by anion post-synthetic exchange(PSE),which were further confirmed by single-crystal to single-crystal transformation(SCSC)and by products that were characterized by multiple techniques including CO2 adsorption measurements at 195 K,19F NMR spectra,Fourier transform infrared(FT-IR)spectra and energy-dispersive spectroscopy(EDS).The adsorption performance of CO2/CH4 and CO2/N2 were determined and comparision between SMOF-SIFSIX-1 and SMOF-GeFSIX-1,and the breakthrough experiments were performed to further evaluated the actual separation property.Furthermore,the adsorption thermodynamics of SMOF-GeFSIX-1 for C2H2/C2H4 and C2H2/CO2 mixtures was determined.The IAST selectivity of CO2/CH4(50:50)and CO2/N2(15:85)is calculted to be 9.9 and 80.2 at 273 K and 100 kPa for SMOF-GeFSIX-1,which is lower to the selectivity of SMOF-SIFSIX-1(21.1 and 131.7).The dynamic breakthough tests revealed that the captured amount of CO2 gas were reached 0.64 mmol/g and 0.70 mmol/g for CO2/CH4(50:50)and CO2/N2(15:85)binary mixtures for SMOF-SIFSIX-1,similarity for SMOF-GeFSIX-1 with the uptake of 0.68 mmol/g and 0.89 mmol/g,confirming that SMOF-SIFSIX-1 and SMOF-GeFSIX-1 has potential application for adosrbing CO2 in preference to CH4 and N2.Moreover,as for C2H2/C2H4(50:50),the IAST selecitvity of SMOF-GeFSIX-1 at 298 K and 100 kPa is 5.7,lower than SMOF-SIFSIX-1.Nevertheless,the IAST selecitvity of C2H2/CO2(50:50)reaches 8.8,which is superior to SMOF-SIFSIX-1(4.9).The SMOFs materials of SMOF-PFSIX-1 and SMOF-AsFSIX-1 have been established for the first time via introduced PF6-and AsF6-,and the selectivity separation for CO2/CH4/N2,Xe/Kr,and C3H6/C3H8 of the two SMOFs materials were studied.The results revealed that SMOF-PFSIX-1 and SMOF-AsFSIX-1 are the isotucture materials with the 3D pore windows of the sizes betwwen 1.8 A-5.5 A,which have been confirmed the permanenty porosity with the BET surface area of 389 m2/g and 422 m2/g.The adsorption behaivous of CO2/CH4(50:50)was further assessed for SMOF-PFSIX-1 and SMOF-AsFSIX-1 with the IAST selectivity of 27.3 and 36.4 at 273 K and 100 kPa.As for the CO2/N2(15:85),SMOF-PFSIX-1 and SMOF-AsFSIX-1 show excellent performance with the IAST selectivity of 293.2 and 225.1,only relative lower to the highest selectivity of IISERP-HOF1.The fixed-bed breakthrough tests were employed to verify the outperforming separations of SMOF-PFSIX-1 and SMOF-AsFSIX-1 for CO2/CH4(50:50,v/v)and CO2/N2(15:85,v/v).Besides,at room conditions,SMOF-PFSIX-1 and SMOF-AsFSIX-1 also have superior performance of Xe/Kr(20:80)with the IAST selecitvity of 6.87 and 6.72,exceeding the HOF-BTB,which is the highest among the HOFs.The feasibility of SMOF-PFSIX-1 and SMOF-AsFSIX-1 for their industrial application was also verified by dynamic experimental breakthough of Xe/Kr(20:80,v/v).As for the C3H6/C3H8,the IAST selecitvity of C3H6/C3H8(50:50)for SMOF-PFSIX-1 is up to 140.8,which is significantly higher than SMOF-AsFSIX-1 and other HOFs materials.