Preparation of single atom catalysts (SACs) is of broad interest to materials scientists and chemists but remains a formidable challenge. Herein, we develop an efficient approach to synthesize SACs via a precursor-dilution strategy, in which metalloporphyrin (MTPP) with target metals are co-polymerized with diluents (tetraphenylporphyrin, TPP), followed by pyrolysis to N-doped porous carbon supported SACs (M 1 /N-C). Twenty-four different SACs, including noble metals and non-noble metals, are successfully prepared. In addition, the synthesis of a series of catalysts with different surface atom densities, bi-metallic sites, and metal aggregation states are achieved. This approach shows remarkable adjustability and generality, providing sufficient freedom to design catalysts at atomic-scale and explore the unique catalytic properties of SACs. As an example, we show that the prepared Pt 1 /N-C exhibits superior chemoselectivity and regioselectivity in hydrogenation. It only converts terminal alkynes to alkenes while keeping other reducible functional groups such as alkenyl, nitro group, and even internal alkyne intact.

No abstract

Two new moisture- and air-stable bis(β-ketoamino)nickel(II) complexes Ni[R1C(O)CHC(NAr)R2]2 (Ar ≡ 2,6-iPr2C6H3; R1 = R2 = CH3, 1; R1 = C6H5, R2 = CH3, 2), together with the moderately stable complex Ni2[CH3C(O)CHC(O)CH3]4[H2NtBu]2 (3), which bears a monoanionic O,O-chelate bidentate β-diketone and an sp3-N atom of tBuNH2 mixed ligands, were synthesized and characterized. The solid-state structures of the complexes have been determined by single-crystal X-ray diffractions. Additionally, these new complexes act as catalyst precursors for methyl methacrylate polymerization after activation with methylaluminoxane (MAO). The polymers obtained by 1 and 2 show broader polydispersity than that obtained by 3. 13C NMR analyses indicate that these catalytic systems initiate MMA polymerization to yield PMMA with rich syndiotacticity microstructure.

Catalytic conversion of biomass-derived 5-hydroxymethylfurfural (HMF) into high-quality biofuel 2,5-dimethylfuran (DMF) is significant for the utilization of biomass but remains a substantial challenge. Herein, we report a straightforward, eco-friendly, and scalable ball milling method for the synthesis of Co-alloyed Pt (Pt1/Co) single-atom alloy (SAA) catalysts at kilogram levels. The catalysts exhibit superior catalytic performance for the hydrodeoxygenation of HMF to DMF, obtaining 100% HMF conversion and 92.9% selectivity to DMF under 1.0 MPa H2 at 180 °C for 2 h. The reaction pathway is also investigated, which shows that the hydrogenolysis of the CO bond in HMF to form 2,5-dihydroxymethylfuran is the main route during the hydrodeoxygenation and promoted by the synergistic effect of Pt and Co. Pt1/Co SAA catalysts display excellent stability without aggregation after five successive runs. More inspiringly, our method achieves the mass production of Pt1/Co at the kilogram scale, rendering its potential for practical applications. Moreover, by varying acetylacetonate precursors, we show the general synthesis of different Co-supported noble metal SAA catalysts (M1/Co, M = Pd, Ru, Ir, and Rh). Our findings not only offer a facile and readily scalable synthetic approach of SAA catalysts but also open new avenue to the exploitation of biomass.

The growth of semiconducting single-walled carbon nanotubes (s-SWNTs) on flat substrates is essential for the application of SWNTs in electronic and optoelectronic devices. We developed a flexible strategy to selectively grow s-SWNTs on silicon substrates using a ceria-supported iron or cobalt catalysts. Ceria, which stores active oxygen, plays a crucial role in the selective growth process by inhibiting the formation of metallic SWNTs via oxidation. The so-produced ultralong s-SWNT arrays are immediately ready for building field effect transistors.