Design,Synthesis And Gases Sorption Performances Of Acylamide-modified Porous Coordination Polymer

Emerged as a new kind of porous materials with periodic network structure,porous coordination polymers?PCPs??also known as Metal-Organic Framework,MOFs?are formed of multidentated organic ligands included nitrogen and oxygen and metal ions?or metal ion clusters?by self-assembly.In addition to aromatic acids,there are many kinds of organic ligands in coordination polymers,included most of the bases and esters.The porous materials can be designed and synthesized directionally because of the specicial properties of ordered pore structure,tunable pore size and functional group.Porous coordination polymers are new functional molecule materials,which have been developed rapidly and received extensive attention and research in the past twenty years.The reduction of greenhouse gas CO₂ emissions is currently a major target worldwide and porous coordination polymers show great promise for potential applications in CO₂ capture and separation?CCS?due to the high internal surface areas,tunable pore sizes and designable pore environments.In pursuing new high-performance CO₂ gas storage/separation materials,we have designed and synthesised an organic ligand(5,5',5"-??triphenylene-2,6,10-tricarbonyl?tris?azanediyl?triisophthalic acid,H6L1?modified by acylamide,an organic ligand?5,5',5''-??1E,1'E,1''E?-???benzene-1,3,5-triyltris?methylene??tris?oxy??tris?benzene-4,1-diyl??tri s?diazene-2,1-diyl??triisophthalic acid,H6L2?modified by methoxy group and azo group and a organic ligand?5,5'-?carbonylbis?azanediyl??diisophthalic acid,H4L?modified by ureido.Then we synthetise a newly non interpenetrated?3,24?-connected rht-type acylamide-functionalized porous coordination polymer,termed HNUST-5?HNUST denotes Hunan University of Science and Technology?,designed from a nanosized acylamide-linking hexacarboxylate ligand H6L1 and paddlewheel [Cu2?COO?4] secondary building units?SBUs?,a newly non interpenetrated?2,3,4?-c 6-nodal net ureido-functionalized porous coordination polymer,temed HNUST-6,designed from a carbamido-linking tetracarboxylate ligand H4 L and paddlewheel [Cu2?COO?4] secondary building units?SBUs?.Subsequently,we use a series of means to characterize the stuctures of the three ligands and the two porous coordination polymers of HNUST-5 and HNUST-6 and the gases sorption performances of the porous cordination polymer HNUST-5.Similar to Cu-TPBTM,Cu-FTDTT and other reported?3,24?-connected frameworks,there are three types of cages,namely,cuboctahedron?cub-Oh?,truncated tetrahedron?T-Td?,and truncated octahedron?T-Oh?in porous coordination polymers of HNUST-5 with a 1:2:1ratio.The total accessible volume in fully desolvated HNUST-5 is up to 75.8% and the calculated density is only 0.545 g cm-3 as determined by PLATON/VOID routine after the solvent guest molecules and water molecules involved in coordination are removed,highlighting the extremely porous nature of the framework.To the best of our knowledge,HNUST-5 possesses the second highest BET surface area of 3643 m2 g-1 among acylamide-functionalized porous coordination polymers reported to date,as well as large CO₂ uptake capability?38.9 and 24.9 mmol g-1under 36 bar,30.4 and 20.9 mmol g-1 under 20 bar?with excellent selectivity of CO₂/CH4?7.3 and 5.6?and CO₂/N₂?32.5 and 21.9?at 273 and298 K.Additionally,HNUST-5 demonstrates large and selective CO₂ adsorption at near ambient temperature.The Qst of CO₂ is 25.3 kJ mol-1 at the zero coverage.HNUST-5 exhibits a weaker CH4 binding affinity than CO₂ throughout the adsorption process with the Qst value of only 17.7 kJ mol-1 at zero coverage.There may be two reasons why the material have a larger adsorption selectivity of CO₂ gas.One is that the amide functional groups in the framework are used as bridging groups,which can greatly expand the porosity of the framework,increase the specific surface area of BET and pore volume for improving the adsorption capacity of CO₂.The other is that the amide functional group has a large dipole distance,which is favorable for the formation of strong dipole quadrupole interaction with CO₂ and increasing the interaction between materials and CO₂ to improve the adsorption selectivity of CO₂.In summary,in order to increase the pore volume and specific surface area of the porous coordination polymer and the storage capacity and adsorption selectivity of CO₂,the insert of polar functional groups such as acylamide group and oxalamide group is an effective strategy.It has not only laid a foundation for the synthesis of porous coordination polymer with high specific surface area,but also provided a new idea for the design and synthesis of new high-performance CO₂ gas storage /separation materials in the future.