Structural Regulation And Electrochemical Properties Of Metal-calixarene Coordination Cages

Thiacalix[4]arene and its derivatives have strong multichelating sites to metal ions and changeable conformations,which enables them effective ligands to build polyhedral coordination clusters.In this paper,a series of metal-calixarene coordination cages were constructed by p-tert-butylthiacalix[4]arene(H₄TC4A)/p-tert-butylsulfonylcalix[4]arene(H₄TC4A-SO₂)and auxiliary organic ligands containing nitrogen and carboxylic acid.The clusters were characterized by X-ray single crystal diffraction(SC-XRD),PXRD,TGA,FT-IR and other methods.The electrochemical oxygen evolution reaction properties of the complexes were dicusssed by analyzing the structures.1.Four cage cluster compounds with regular octahedral configuration were obtained by self-assembly of H₄TC4A or H₄TC4A-SO₂,pyridine tricarboxylic acid,and Co and Ni metal sources,respectively.The structures were determined by single crystal X-ray diffraction.The oxygen evolution reactivity(OER)experiments were performed by loading the cage clusters directly on carbon paper(CP).For those clusters with the same metal sources,the innercavity of the cage clusters constructed by H₄TC4A-SO₂ are larger than that of H₄TC4A,which can provide more catalytic reaction sites,and the catalytic performance of OER is also stronger accordingly.The OER performances can also be promoted by post-modification of Ag on the cage windows by oxygen and nitrogen coordination.2.Two octahedral cage clusters Ni₂₀ and Ni₂₂ were fabricated from modular construction strategy by[4+2+8]or[2+4+8]condensing modes from Ni₃,Ni₄-thiacalixarene second building units and auxiliary ligands,respectively.The cage clusters have been directly utilized as OER catalysts and showed overpotentials as low as 264.8 m V for Ni₂₀ and 226.8 m V for Ni₂₂ at 10.0 m A/cm~2 under alkaline condition.The performance of Ni₂₂ is confirmed as one of the best pure-metal-phase electrocatalysts for OER.The mechanism of OER was investigated by means of MALDI-TOF,XPS,EDS,SEM and other characterization methods.To further explore the catalytic nature of crystals,an octahedral coordination cage Ni₂₄ based on Ni₄-TC4A SBUs was synthesized with Trimesic acid auxiliary ligand.The less metal active sites make the Ni₂₄ with overpotentials of 390 m V at 10.0m A/cm~2.