Correlation of Mesh Size of Metal–Carboxylate Layer with Degree of Interpenetration in Pillared-Layer Frameworks

Two porous cobal–organic frameworks showing threefold interpenetration of pillared-layer structures, constructed from two-dimensional (2D) neutral metal–carboxylate layers and neutral bis-pyridyl-bis-amide pillars, were hydro­(solvo)­thermally synthesized and structurally characterized by single-crystal X-ray diffraction. Compound {[Co₂(thdc)₂(bpda)₂(DMF)]·2DMF}_<i>n</i> (<b>1</b>, thdc = 2,5-thiophenedicarboxylate; bpda = <i>N,N</i>′-bis­(4-pyridinyl)-1,4-benzenedicarboxamide) adopts a uninodal 6-connected three-dimensional (3D) framework with a {4¹²·6³}-<b>pcu</b> topology in which 2D rhomboid-like 4⁴-<b>sql</b> Co–thdc layers are pillared by bpda ligands. While compound {[Co₃(btc)₂(bpda)₃]·2DMF·9H₂O}_<i>n</i> (<b>2</b>, btc = 1,3,5-benzenetricarboxylate) is composed of a binodal (3,4)-connected 3D framework with a (6³)₂(6⁴·8·10)₃ topology that can be described in terms of two building subunitsa 2D porous honeycomb-like 6³-<b>hcb</b> Co–btc layer and a bpda pillar. An in-depth analysis showed that the mesh size of the metal–carboxylate layer, in addition to the pillar length, is highly correlated with the degree of interpenetration in the pillared-layer framework. The structural characteristics of frameworks <b>1</b> and <b>2</b> fully support this relationship

Cooperative Effect of Unsheltered Amide Groups on CO₂ Adsorption Inside Open-Ended Channels of a Zinc(II)–Organic Framework

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}_<i>n</i> (<b>1</b>, BDC = 1,4-benzyl dicarboxylate, BPDA = <i>N,N′</i>-bis­(4-pyridinyl)-1,4-benzenedicarboxamide). Compound <b>1</b> consists of 4⁴-<b>sql</b> [Zn₄(BDC)₄] sheets that are further pillared by a long linker of BPDA and forms a 3D porous framework with an α-Po 4¹²·6³ topology. Remarkably, the unsheltered amide groups in <b>1</b> 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 <b>1</b> 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 <b>1</b> permits the slipped-parallel arrangement of CO₂ molecules, an arrangement found in crystal and gas-phase CO₂ dimer

Cooperative Effect of Unsheltered Amide Groups on CO₂ Adsorption Inside Open-Ended Channels of a Zinc(II)–Organic Framework

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}_<i>n</i> (<b>1</b>, BDC = 1,4-benzyl dicarboxylate, BPDA = <i>N,N′</i>-bis­(4-pyridinyl)-1,4-benzenedicarboxamide). Compound <b>1</b> consists of 4⁴-<b>sql</b> [Zn₄(BDC)₄] sheets that are further pillared by a long linker of BPDA and forms a 3D porous framework with an α-Po 4¹²·6³ topology. Remarkably, the unsheltered amide groups in <b>1</b> 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 <b>1</b> 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 <b>1</b> permits the slipped-parallel arrangement of CO₂ molecules, an arrangement found in crystal and gas-phase CO₂ dimer