Constructing High Performance Propane-selective Adsorbent Based On Secondary Building Unit Tuning

Propane and propylene are important petrochemical raw materials.The former is derived from natural gas processing or crude oil refining,and the latter is mainly obtained through the purification of C3 cracked gas.Efficient separation of propane from natural gas or C3 cracked gas is the key to the process of propane recovery and propylene purification.This work revolves around this major industrial demand,proposes a secondary building unit（SBU）control strategy for MOFs materials,and prepares a series of high-performance zirconium-based MOFs adsorbents to realize the efficient chemical separation process of propane recovery and propylene purification under normal temperature.The main results include the following 4aspects:First,using s-triazine to replace the coordinated water molecules in the SBU of Zr-TBAPy（NU-1000）to strengthen the pores and alkanes to form a basic surface chemical microenvironment of C–H^δ+···N^δ-electrostatic interaction,and obtain TZ@Zr-TBAPy with stronger adsorption separation performance.Under normal temperature and pressure,the IAST selectivity of C₃H₈/CH₄ and C₂H₆/CH₄ of TZ@Zr-TBAPy material is as high as 1518 and 11.7,respectively.It is one of the materials with the best performance for propane/methane adsorption and separation that has been reported internationally.This work shows that SBU control can enhance the adsorption and separation performance of propane recovery from natural gas by modifying the surface electrostatic environment of MOFs pores.Second,on the basis of the above work,the use of more sterically hindered melamine（MA）to modify the SBU of Zr-TBAPy,further strengthen the material alkaline surface chemical microenvironment,and obtain a new type of MA@Zr-TBAPy adsorbent.Under normal temperature and pressure,the IAST selectivity of C₃H₈/CH₄ and C₂H₆/CH₄ of MA@Zr-TBAPy material is as high as 1586 and 18.73,this work shows that SBU control can modify the surface electrostatic environment of MOFs pores,and at the same time strengthen the steric hindrance effect of pores on the adsorbate,and further enhance the adsorption and separation performance of propane recovery from natural gas.Third,starting from the design of selective surface chemistry for alkanes based on molecular simulations,coordination modification of two-dimensional g-C₃N₄ rich in nitrogen heteroatoms into the SBU of Zr-BPDC,prepared the first propane selective g-C₃N₄@Zr-BPDC adsorbent with independent intellectual property rights.This material preferentially adsorbs propane from propylene,and the adsorption capacity for propane at room temperature and pressure is 8.79 mmol/g,DFT calculations show that propane selectivity comes from the more effective multiple C–H^δ+···N^δ-interactions between propane and adsorbent nitrogen atoms.Fourth,a basic molecular chain with enhanced propane selectivity is constructed in Zr-BPDC through a covalent coupling reaction,and a new type of GMA@Zr-BPDC material with further improved propane selectivity is obtained.Under normal temperature and pressure,the adsorption capacity of GMA@Zr-BPDC material for propane reaches 10.17 mmol/g,which is19.6%higher than that of Zr-BPDC.More importantly,its propane/propylene selectivity is as high as 1.8,which is the frontier of the reported performance of propane selective adsorbents.