文摘
A unique spatial arrangement of amide groups for CO2 adsorption is found in the open-ended channels of a zinc(II)鈥搊rganic framework {[Zn4(BDC)4(BPDA)4]路5DMF路3H2O}n (1, BDC = 1,4-benzyl dicarboxylate, BPDA = N,N鈥?/i>-bis(4-pyridinyl)-1,4-benzenedicarboxamide). Compound 1 consists of 44-sql [Zn4(BDC)4] sheets that are further pillared by a long linker of BPDA and forms a 3D porous framework with an 伪-Po 412路63 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.