Perfor Mance Enhancement Of Thermo Chemical Energy Storage Materials Based On Metal Organic Framework Water System

With the development of society,the efficient and clean utilization of energy is becoming more and more important.Thermochemical energy storage is becoming one of the important solutions to solve the energy crisis and energy efficient utilization.Adsorption thermochemical energy storage scheme has been widely concerned because of its advantages of high energy storage density,low heat loss,long-term heat storage and long-distance heat transfer.Among the adsorptive thermochemical energy storage materials,metal organic frameworks(MOFs)have attracted much attention due to their abundant adjustable pore structures,flexible functionalization,excellent adsorption properties and great potential for surface modification.Water is one of the most green adsorption working fluids,and MOFs and water are becoming a research hotspot.The main contents and conclusions of this paper are as follows.(1)The structure and water adsorption properties of MOFs were analyzed by literature review and related data,and the structure-activity relationship was constructed by numerical fitting.The materials with higher water adsorption capacity,better water absorption evaluation,better adsorption hysteresis and excellent structural stability were compared and analyzed.Finally,the materials to be studied were selected according to larger pore volume,suitable charge distribution and matching pore size.Through the trial production and characterization evaluation of the materials,the optimization parameters and methods for water adsorption conditions were determined,including acid environment,synthesis conditions,functional groups,coating structure,optimization of organic ligands,expansion optimization and inorganic salt impregnation optimization.(2)Mil-101(Cr)material was prepared.When the specific surface area,pore volume and maximum water adsorption capacity of the prepared materials are high,the water difusion coefficient remains at a high level.The maximum water adsorption capacity is about 1581.2542 mg/g,which has advantages in related research.The results show that the hydrophilicity of MIL-101(Cr)can be improved by Mg ion substitution.When the mass ratio of Cr to Mg is 1:4,a Cr based composite metal organic framework material MIL-101(Cr,Mg)with excellent properties can be obtained.(3)Adding appropriate amount of acidified MWCNTs and CaCl2 crystal into MIL-101(Cr)can significantly improve the water adsorption performance of the material.In this study,the optimal salt concentration is about 27.3%.Theoretically,about 3 g of acidified MWCNTs doped with MIL-101(Cr)can achieve excellent water adsorption performance,and its heat storage density can reach 450 kWh/kg.Carbon nanotubes calcium chloride MIL-101(Cr)composite has excellent water adsorption capacity and maximum water adsorption capacity at low water pressure,and has low preparation cost,good stability and high heat storage density.It can be an excellent candidate material for adsorption heat pump in the future.(4)The improvement methods of hydrophilic functional group modification,benzoic acid crystal modification and ionic liquid water absorption modification were explored.It is found that the hydrophilic functional groups can improve the water adsorption capacity at low water pressure,benzoic acid can improve the crystal regularity and water adsorption performance,and hydrophilic ionic liquids can improve the organic metal skeleton coating.