title: Alkaline earth metal (Mg, Sr, Ba)-organic frameworks based on 2,2',6,6'-tetracarboxybiphenyl for proton conduction.
abstract: Three new alkaline earth metal based metal-organic frameworks (MOFs), namely M-BPTC (M = Mg, Sr, Ba), have been synthesized by using BPTC (2,2',6,6'-tetracarboxybiphenyl) as ligand under hydrothermal conditions. These MOFs exhibit interesting structural diversity, variable chemical and thermal stability, as well as proton conductivity. Mg-BPTC with the formula {[Mg(BPTC)0.5(H2O)3]·5H2O}n consists of BPTC(4-) extended metal layers, and novel highly ordered infinite tape-like structures of cyclic water octamers reside interlayer. Three-dimensional porous {[Sr2(BPTC)(H2O)6]·H2O}n (Sr-BPTC) features inorganic Sr-O chains (I(1)O(2)) and open hydrophilic channels where water heptamers and carboxyl oxygen atoms conspire to form H-bond networks, whereas 3D {[Ba6(BPTC)3(H2O)6]·11H2O}n (Ba-BPTC) shows Ba-O inorganic layer (I(2)O(1)) and 1D channels incorporating large water 14-mers and 18-mers. M-BPTC (M = Mg, Sr) species exhibit excellent water stability and proton conductivity due to their respective appropriate pathways for proton transporting. M-BPTC (M = Sr, Ba) structures are highly thermally stable due to the presence of the inorganic connectivity. The present results suggest that M-BPTC (M = Mg, Sr) are promising materials for proton conduction and provide insight into the hydrogen bonding motif.
authors.affiliation: College of Chemistry and Molecular Engineering, Zhengzhou University , Science Road No. 100, Zhengzhou 450001, China.
authors.forename: Xi-Yan
authors.initials: XY
authors.lastname: Dong
authors.forename: Xiao-Peng
authors.initials: XP
authors.lastname: Hu
authors.forename: Hong-Chang
authors.initials: HC
authors.lastname: Yao
authors.forename: Shuang-Quan
authors.initials: SQ
authors.lastname: Zang
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Hou
authors.forename: Thomas C W
authors.initials: TC
authors.lastname: Mak