title: Cooperative effect of unsheltered amide groups on CO2 adsorption inside open-ended channels of a zinc(II)-organic framework.
abstract: A unique spatial arrangement of amide groups for CO2 adsorption is found in the open-ended channels of a zinc(II)-organic framework {[Zn4(BDC)4(BPDA)4]·5DMF·3H2O}n (1, BDC = 1,4-benzyl dicarboxylate, BPDA = N,N'-bis(4-pyridinyl)-1,4-benzenedicarboxamide). Compound 1 consists of 4(4)-sql [Zn4(BDC)4] sheets that are further pillared by a long linker of BPDA and forms a 3D porous framework with an α-Po 4(12)·6(3) topology. Remarkably, the unsheltered amide groups in 1 provide a positive cooperative effect on the adsorption of CO2 molecules, as shown by the significant increase in the CO2 adsorption enthalpy with increasing CO2 uptake. At ambient condition, a 1:1 ratio of active amide sites to CO2 molecules was observed. In addition, compound 1 favors capture of CO2 over N2. DFT calculations provided rationale for the intriguing 1:1 ratio of amide sorption sites to CO2 molecules and revealed that the nanochamber of compound 1 permits the slipped-parallel arrangement of CO2 molecules, an arrangement found in crystal and gas-phase CO2 dimer.
authors.affiliation: Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Cheng-Hua
authors.initials: CH
authors.lastname: Lee
authors.forename: Hung-Yu
authors.initials: HY
authors.lastname: Huang
authors.forename: Yen-Hsiang
authors.initials: YH
authors.lastname: Liu
authors.forename: Tzuoo-Tsair
authors.initials: TT
authors.lastname: Luo
authors.forename: Gene-Hsiang
authors.initials: GH
authors.lastname: Lee
authors.forename: Shie-Ming
authors.initials: SM
authors.lastname: Peng
authors.forename: Jyh-Chiang
authors.initials: JC
authors.lastname: Jiang
authors.forename: Ito
authors.initials: I
authors.lastname: Chao
authors.forename: Kuang-Lieh
authors.initials: KL
authors.lastname: Lu