Study Of ¹⁴CH₄ Adsorption And Separation On Metal-organic Frameworks And Synthesis

As carbon isotopes,14C not only has a long half-life,but also the abundance is very stable.However,with the vigorous development of nuclear power,the content of 14C is increasing and it also brings threat to ecological environ.14CH4,as the main 14C gas released by nuclear power,how to efficiently deal is of great significance for the reduction of 14C.In the paper,based on the metal-organic frameworks(MOFs)and computational chemical methods,the adsorption and separation performances of 14CH4 were studied and the synthesis of related materials were explored,aiming to develop a novel material with high 14CH4 adsorption and separation capacity.The main contents and innovations are as follows.Based on the computational chemistry method and PCN-14,containing unsaturated metal sites(Open-Metal Sites,OMS),five kinds of metal modified materials were designed and developed at the molecular level,to form M-PCN-14(M=Cu,Ca,Zn,Ni,Co,Cr)series materials.New force fields,which can accurately describe the adsorption behavior of gas on M-PCN-14 and HKUST-1,were developed.Based on the quantum chemistry and molecular simulation methods,the 14CH4 adsorption and separation behavior on IRMOF-1,IRMOF-3,IRMOF-6,IRMOF-14,HKUST-1 and Cu-PCN-14,which are common MOFs materials and M-PCN-14 series materials are studied.The results show that the OMS has a strong interaction with '4CH4.The 14CH4 storage capacities of MOFs,which have OMS,are all larger than IRMOFs.And the results show 14CH4 adsorption capacity of MOFs materials can be enhanced by introducing electron groups into ligands,and the-C2H4 groups on organic ligands has significant effect on improving the 14CH4 capacity.And tIn above materials,Zn-PCN-14 has the largest volume capacity with 236.9cm3/cm3 in the 298K and 3.5MPa,which is 33 cm3/cm3 larger than Cu-PCN-14.Ca-PCN-14 has the highest gravimetric capacity with 0.284g/g in 298K and 3.5MPa,which is 0.87 g/g larger than Cu-PCN-14.14CH4 separation behavior on Co-PCN-14 is the best,whose adsorption selectivity is between 5.3-4.8 in the pressure range of 1-35bar at 298K.In the research,we explored the synthetic methods of IRMOF-1,HKUST-1 and PCN-14.We investigated the effects of synthesis temperature,time and raw materials ratio on the synthesis of the three materials,which laid the foundation for the development and application of new MOFs materials.When the temperature is lower,the crystallization rate of IRMOF-1 is too slow.For HKUST-1,if the temperature is too high,impurities tend to be generated.The content of HBF4 has a great influence on the synthesis of PCN-14.