Porphyrin-based Coordination Polymer Composed of Layered Pillarless Two-dimensional Networks

Abstract

Single crystals of a layer-structured coordination polymer, BNAS-11 [ZnTCPP(H 2 O)Zn 2 (H 2 O) 2 ] (ZnTCPP: 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrinatozinc(II)), were obtained. Tetratopic ZnTCPP molecules are connected through dimer zinc paddle-wheel secondary building units and form a two-dimensional (2D) network with square grids. The layers are stacked electrostatically without the need of binding pillar ligands.Two-dimensional (2D) nanomaterials with monomolecular thickness are of considerable interest because they exhibit unique properties due to their dimensionality and can be utilized as extremely small components in nanodevices.1 Coordination compounds, including metalorganic frameworks (MOFs) or porous coordination polymers (PCPs), are attractive for assembling 2D nanosheets as their structures can be rationally designed from inorganic and organic building units and are endowed with various functionalities.2,3 We have synthesized 2D MOF nanosheets (NAFS) by a bottom-up approach utilizing reactions at the airliquid interface.4 Molecular building units with peripheral coordinative parts are spread on the surface of an aqueous solution of metal-ion linkers. This initiates a coordinative reaction at the interface and results in the formation of 2D MOF nanosheets. 4 The synthetic protocol is not restricted to MOFs and can be used for the creation of various 2D coordination compounds 5 as the reactants are strictly restricted to the direction parallel to the surface. Another way to obtain 2D nanosheets of various materials (e.g., graphite, 1c metal oxides, 1d transitionmetal chalcogenides, 1e and organic polymers 1f ) is by exfoliating the bulk crystals with layered structures; the starting components are strongly connected laterally, while the 2D layers are weakly stacked, allowing peeling by physical and chemical treatments.(Metallo)porphyrins are stable macrocyclic ligands with square-planar geometry 3c,3d,6 and are excellent candidates for constructing 2D nanonetworks through a suitable choice of peripheral coordinative substituents and metal-ion linkers. However, it is difficult to exfoliate MOF crystals as removal of the counter ions needed for charge balance destabilizes the peeled layers 3e3g or the individual layers are rigidly connected vertically by bidentate pillars.3h,3i On the other hand, porphyrinbased MOF crystalline materials without any pillars, reminiscent of the interlayer stacking mode of the NAFS nanofilms, 4 grown by the LangmuirBlodgett layer-by-layer (LB-LbL) methodology are rare. 3j,3kHere we report the isolation of a new bulk analogue of crystalline NAFS thin films [ZnTCPP(H 2 O)Zn 2 (H 2 O) 2 ] (designated BNAS-11). It is a polymorph of the PPF-1 MOF, 3k retaining the same ZnTCPPZn sheet structure but adopting a different stacking sequence perpendicular to the layers. The existence of such multiple polymorphs with differing sheet stacking patterns reflects the weak interlayer interactions and provides opportunities for facile exfoliation of the crystals to obtain 2D nanosh...

A single crystalline porphyrinic titanium metal–organic framework

“…The overall structure is simplified into a novel (4, 6) connected net with a point symbol of {4 4 ·6 2 } 3 {4 9 ·6 12 } 2 , which has never been reported to the best of our knowledge. 37 , 38 …”

“…The overall structure is simplied into a novel (4, 6) connected net with a point symbol of {4 4 $6 2 } 3 {4 9 $6 12 } 2 , which has never been reported to the best of our knowledge. 37,38 The phase purity of PCN-22 was conrmed by comparison of the powder X-ray diffraction pattern and the simulated pattern from the crystal structure (Fig. S5 †).…”

Synthesis and characterizations of a paddlewheel-type dirhodium-based photoactive porous metal-organic framework

“…The distribution of pore diameter, estimated using the Horvath-Kawazoe (HK) method, suggested that [1] has pores of approximately 4.7 Å in size similar to [Zn 2 (ZnTCPP)] (ca. 4.4 Å) of which value was estimated from the single crystal X-ray structures [26][27]. These results clearly indicated that [1] has a porous framework structure and sufficient micropores to permit N 2 gas adsorption.…”

Open MOFs with Unique Hexatopic Zinc-5,15-bis(4′-carboxyphenyl)-10,20-bis(3′,5′-dicarboxyphenyl)porphyrin Linker

“…By employing Zn(II) as the connecting node, H 6 HCPP forms Zn 2 paddlewheels in Zn-hcMPF (3) and the structural features are similar to Mn 2 paddlewheels in Mn-hcMPF (1). BNAS-11 47 and MMPF-4 48 represent the corresponding frameworks built by H 4 TCPP and H 8 OCPP, respectively. The former is a 2D layered polymer featuring Zn 2 paddlewheels, while the latter is a highly symmetrical pcu topological network built by Zn 2 dimers.…”