Alkali Metal Cation(K+,Cs+)Induced Dissolution/Reorganization of Porous Metal Carboxylate Coordination Networks in Water

摘要

Porous metal-organic coordinationnetworks(MOCNs){A2[M3-ACHTUNGTRENUNG(btec)2ACHTUNGTRENUNG(H2O)4]}n(1,A=K,M=Co;2,A=K,M=Ni;3,A=Cs,M=Co;and4,A=Cs,M=Ni;btec=benzene- 1,2,4,5-tetracarboxylate)with nearlyidentical structural features were hydrothermallyprepared.These compoundsadopt(4,8)-connected scu nets but exhibit subtle differences in the topology of the final three-dimensionalarchitectures.Compound 1 has a regularnet with the largest solvent void(21.1%),while the nets of the otherthree(2-4)are slightly distorted from aregular shape and have malformedpores with smaller solvent voids(5.4-11.4%).Likely, the different supramolecular environments among 1-4subtly depend on the eight-connected binodal cubical vertices/four-connectedsquare-planar connectivity between the trimetallic clusters and the btec ligands.Cobalt species 3 dissolved in an aqueoussolution of KCl,and then reorganized to form 1 at ambient temperature.Interestingly,under similar conditions,1 dissolved and then was regenerated to give the same structure.Nickel species2 and 4 also underwent a dissolution/ reorganization process in an aqueoussolution of KCl to afford new metal-carboxylate product {K2ACHTUNGTRENUNG[Ni3-ACHTUNGTRENUNG(btec)2ACHTUNGTRENUNG(H2O)4]}n(2’).This compoundforms a(4,8)-connected scu net withregular pores,which is isostructural and isomorphous with 1, and is a supramolecularisomer of 2.Similarly,in anaqueous solution of CsCl,1-4 wereconverted to 1D zigzag chain structures{Cs2[MACHTUNGTRENUNG(btec)ACHTUNGTRENUNG(H2O)4]}n(5,M=Co;6,M=Ni)that enlarged to hydrogenbonded3D porous supramolecular networks.Remarkable, reversible alkalimetal cation induced structural transformationsbetween 1 and 5occurredviadissolution/reorganizationprocesses.Thermogravimetric analyses showedthat these metal-carboxylate specieshave high thermal stability(T>300 8C).