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exhibit photocatalytic hydrogen evolution in 2009, [12] and many advances have been made since then. [13,14] After the potential of g-C 3 N 4 was first observed, while focusing on the hydrogen evolution half-reaction, interest has begun to shift to achieving overall water splitting using these materials. [15,16] However, the exact structure of most g-C 3 N 4 materials is unknown and the synthesis usually involves high temperature processing, which offers limited scope for fine-tuning structure and properties. Also, while g-C 3 N 4 can be produced from inexpensive starting materials, the synthetic yield of the material is typically low. [15,17] Of special relevance here, graphitic carbon nitrides are insoluble solids: as for many inorganic catalysts, this can present challenges in terms of processing.Rather few organic photocatalysts have been studied for hydrogen evolution other than g-C 3 N 4 . Recently, nitrogencontaining poly(azomethine) networks and covalent triazinebased frameworks (CTFs) were shown to have photocatalytic activity with the addition of platinum cocatalysts. [18,19] We have shown that a series of conjugated microporous polymers (CMPs) could facilitate hydrogen evolution from water in the presence of a sacrificial electron donor, without any additional heavy metal cocatalyst. [20,21] Other CMPs have since been studied for photocatalysis [22,23] and recent studies have demonstrated that linear conjugated polymers can have high photocatalytic activities. [24,25] However, as with g-C 3 N 4 , none of these organic materials are soluble in common organic solvents. This insolu bility makes it more challenging to process these materials into functional composites. Moreover, photocatalysts are typically kept in suspension by stirring to prevent sedimentation, which results in loss of photocatalytic activity. [26] The loss of activity of insoluble catalysts can be prevented with the use of support substrates, [27] however, using solution processability allows the use of simpler supports and easier development of photoelectrodes.Soluble oligo(phenylene)s have been previously reported as photocatalysts, however, they displayed low activity, were only active under UV light, required a Ru cocatalyst and were only poorly soluble in organic solvents limiting processability. [28] More recently soluble metal-chelating polymers have been prepared although the photocatalytic activity of these polymers also appear to be very low with apparent quantum yields (AQY) below 3 × 10 −4 %. [29] The solubility of some alkylated conjugated polymers has also facilitated the preparation of polymer nanoparticles (PDots). [30,31] The preparation of these PDots enabled significant enhancements in rate over the pristine polymer although scalability and long-term stability of this approach has yet to be shown. Direct photocatalytic water splitting is an attractive strategy for clean energy production, but multicomponent nanostructured systems that mimic natural photosynthesis can be difficult to fabricate because of the insolubil...

[Mn(bpy)(CO)3Br] cast in a Nafion membrane is an active heterogeneous electrocatalyst with good selectivity for CO2 reduction to CO in neutral aqueous electrolyte. Addition of multi-walled carbon nanotubes (MWCNT) leads to a ∼10 fold current enhancement and stable CO : H2 yields (1 : 2) at -1.4 V vs. Ag/AgCl at pH 7.

Immobilization of [Mn(bpy)(CO)3Br], (1) and [Mn(bpy((t)Bu)2)(CO)3Br] (2, where (bpy((t)Bu)2) = 4,4'-di-tert-butyl-2,2'-bipyridine) in Nafion/multi-walled carbon nanotubes (MWCNT) on glassy carbon yielded highly active electrodes for the reduction of CO2 to CO in aqueous solutions at pH 7. Films incorporating have significantly improved selectivity towards CO2, with CO : H2 ∼ 1 at -1.4 V vs. SCE, exceeding that for the previously reported /MWCNT/Nafion electrode. Furthermore, we report the synthesis and subsequent electrochemical characterization of two new substituted Mn(i) bipyridine complexes, [Mn(bpy(COOH)2)(CO)3Br] (3) and [Mn(bpy(OH)2)(CO)3Br] (4) (where (bpy(COOH)2) = 4,4'-di-carboxy-2,2'-bipyridine and (bpy(OH)2) = 4,4'-di-hydroxy-2,2'-bipyridine). Both 3 and 4 were found to have some activity towards CO2 in acetonitrile solutions; however once immobilized in Nafion membranes CO2 reduction was found to not occur at significant levels.