Control over the architectural and electronic properties of heterogeneous catalysts poses a major obstacle in the targeted design of active and stable non-platinum group metal electrocatalysts for the oxygen reduction reaction. Here we introduce Ni3(HITP)2 (HITP=2, 3, 6, 7, 10, 11-hexaiminotriphenylene) as an intrinsically conductive metal-organic framework which functions as a well-defined, tunable oxygen reduction electrocatalyst in alkaline solution. Ni3(HITP)2 exhibits oxygen reduction activity competitive with the most active non-platinum group metal electrocatalysts and stability during extended polarization. The square planar Ni-N4 sites are structurally reminiscent of the highly active and widely studied non-platinum group metal electrocatalysts containing M-N4 units. Ni3(HITP)2 and analogues thereof combine the high crystallinity of metal-organic frameworks, the physical durability and electrical conductivity of graphitic materials, and the diverse yet well-controlled synthetic accessibility of molecular species. Such properties may enable the targeted synthesis and systematic optimization of oxygen reduction electrocatalysts as components of fuel cells and electrolysers for renewable energy applications.

We show that structural changes of a guest molecule can trigger structural transformations of a crystalline host framework. Azobenzene was introduced into a flexible porous coordination polymer (PCP), and cis/trans isomerizations of the guest azobenzene by light or heat successfully induced structural transformations of the host PCP in a reversible fashion. This guest-to-host structural transmission resulted in drastic changes in the gas adsorption property of the host-guest composite, displaying a new strategy for creating stimuli-responsive porous materials.

Condensation of ortho--phenylenediamine deriv--atives with ortho--quinone moieties at edge planes of graphitic carbon generates graphite--conjugated pyrazines (GCPs) that are active for oxygen reduction electrocatalysis in alkaline aqueous electrolyte. Catalytic rates of oxygen reduction are positively correlated with the electrophilicity of the active site pyrazine unit, and can be tuned by over 70 fold by appending electron--withdrawing substituents to the phenylenediamine precursors. Discrete molecular analogs containing pyrazine moieties display no activity above background under identical conditions. This simple bottom up method for constructing molecularly well--defined active sites on ubiquitous graphitic solids enables the rational design of tunable heterogeneous catalysts.The interconversion of electrical and chemical energy re--quires the coupling of electron transfer with substrate bond rearrangement. This can be achieved at surface exposed active sites of heterogeneous electrocatalysts 1 or via redox mediation facilitated by a homogeneous molecular electrocatalyst. 2 Mo--lecular electrocatalysts yield readily to synthetic alteration of their redox properties permitting systematic tuning of catalyst activity and selectivity. 3 Similar control is difficult to achieve with heterogeneous electrocatalysts because they typically exhibit a distribution of active site geometries and local elec--tronic structures, 4 which are recalcitrant to molecular--level synthetic modification. However, heterogeneous electrocata--lysts typically exhibit greater durability and are more readily integrated into functional energy conversion devices such as fuel cells and electrolyzers. In principle, the attractive features of heterogeneous and molecular catalysts could be combined if robust methods are developed for constructing well--defined, tunable active sites on the surfaces of conductive solids.Typically, molecular electrocatalysts are heterogenized by introducing an inert tether between the active site and the electrode surface. 5 However, there exist a paucity 6 of surface connection chemistries that are both robust and well--defined. For example, thiol--based self--assembled monolayers provide for a high degree of surface uniformity, 7 but exhibit a limited range of electrochemical stability. 8 In contrast, harsher liga--tion methods involving electrogenerated radicals 9 forge ro--bust covalent linkages with carbon surfaces but are prone to form ill--defined polymeric multilayers and are incompatible with sensitive molecular functionality. 9 Additionally, these methods inherently impose a tunneling barrier for electron transfer, limiting the rate of electron flux to the active site.Herein, we introduce an orthogonal strategy for constructing molecularly well--defined surface active sites that exploits the native surface chemistry of graphitic carbon, obviating the need for an exogenous linker. We show that condensation of ortho--phenylenediamines with ortho--quinone moieties pre--sent on the edge planes of ...

Control of the physical and chemical properties of porous materials has been an ongoing challenge for the optimization of functions, such as gas storage, separation, and catalysis. For example, a high surface area is important for large-volume gas uptake, and the control of pore shape is also significant for molecular separation.[1] These requirements are also valid for porous coordination polymers (PCPs) or metal-organic frameworks (MOFs), which consist of metal ions and organic linkers.[2] This class of adsorbent has received attention because of its structural versatility and physical properties, such as magnetism and redox activity.[3] Among the PCP compounds, flexible frameworks have been identified as a unique type of porous material because of their guestresponsive transformations.[4] This structural transformation is often directly related to the functionality of these frameworks; gas recognition separation or slow drug release are good examples in this respect. [5] The flexibility of the network must be modulated to precisely control these functions and to tailor the network performance, and much effort has been expended in creating flexible compounds.[6] However, there have been few reports on the rational incorporation of flexibility in the known PCP compounds as their synthesis is difficult.[7] Herein, we describe the preparation of ligand-based solid solutions of flexible PCPs and our attempts to overcome difficulties in the precise flexibility control and resulting gas sorption properties. A few approaches toward ligand-based solid solutions of robust metal-organic framework have been reported, [8] although corresponding structural information and control of their adsorptive functions has not been observed. We have synthesized two distinct interdigitated frameworks that contain different organic ligands, and have created a series of solid solutions based on these frameworks. These compounds exhibited a range of flexible adsorption properties, and their bimodal properties enabled them to show an improved performance compared with the two pure compounds CID-5 and CID-6 in the separation of a CO 2 /CH 4 mixture.The two flexible compounds with an interdigitation motif of 2D layers, [{Zn(5-NO 2 -ip)(bpy)}(0.5DMF·0.5MeOH)] n (CID-5'G; 5-NO 2 -ip = 5-nitroisophthalate, bpy = 4,4'-bipyridyl, and CID = coordination polymer with an interdigitated structure), and [{Zn(5-MeO-ip)(bpy)}(0.5 DMF·0.5 MeOH)] n (CID-6'G; 5-MeO-ip = 5-methoxyisophthalate), were prepared from Zn(NO 3 ) 2 ·6 H 2 O and either of the ligands in a 1:1 v/v DMF/MeOH mixture. The crystal structures are shown in Figure 1. For both compounds, two carboxylate groups coordinate to Zn 2+ ions to form eight-membered rings, and the bpy groups coordinate to the axial position of the Zn 2+ ions to create the 2D layered structure. The layers are assembled in an interdigitated fashion with micropores formed within the structure. Both frameworks can be

A new porous coordination polymer, ([La(BTB)H 2 O] · solvent ( 1 ⊃ ⊃ guest)), is synthesized. Gas adsorption, ideal adsorbed solution theory (IAST) and breakthrough experiments of it exhibits high CH 4 separation capability toward CO 2 and C2 hydrocarbons at 273 K. In addition, this also shows good water and chemical stability, in particular, it is stable at pH = 14 at 100 ° C, which is unprecedented for carboxylate-based porous coordination polymers. Furthermore, the effective adsorption site for separation is revealed by using an in situ diffuse refl ectance IR fourier transform (DRIFT) spectra study.

5Gas separation properties of CH 4 /CO 2 and CH 4 /C 2 H 6 for flexible 2D porous coordination polymers under equilibrium gas condition and mixture gas flowing condition were investigated and the gas separation efficiencies were optimized by precise tuning of flexibility in ligand-base solid solution compounds. Notes and references70

Rational design to control the dynamics of molecular rotors in crystalline solids is of interest because it offers advanced materials with precisely tuned functionality. Herein, we describe the control of the rotational frequency of rotors in flexible porous coordination polymers (PCPs) using a solid-solution approach. Solid-solutions of the flexible PCPs [{Zn(5-nitroisophthalate)x(5-methoxyisophthalate)1-x(deuterated 4,4'-bipyridyl)}(DMF·MeOH)]n allow continuous modulation of cell volume by changing the solid-solution ratio x. Variation of the isostructures provides continuous changes in the local environment around the molecular rotors (pyridyl rings of the 4,4'-bipyridyl group), leading to the control of the rotational frequency without the need to vary the temperature.

A method for the equimolar dehydrogenative coupling of arenes and imides is developed. Under the influence of a ruthenium catalyst over blue-light irradiation, a range of simple and widely available arenes and sulfonimides can be coupled. The reaction was studied with electrochemical techniques, which elucidated a detailed reaction mechanism. This work will accelerate arylamine-based material and biological science.