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Oxygen reduction reaction (ORR) is vital for clean and renewable energy technologies, which require no fossil fuel but catalysts. Platinum (Pt) is the best‐known catalyst for ORR. However, its high cost and scarcity have severely hindered renewable energy devices (e.g., fuel cells) for large‐scale applications. Recent breakthroughs in carbon‐based metal‐free electrochemical catalysts (C‐MFECs) show great potential for earth‐abundant carbon materials as low‐cost metal‐free electrocatalysts towards ORR in acidic media. This article provides a focused, but critical review on C‐MFECs for ORR in acidic media with an emphasis on advances in the structure design and synthesis, fundamental understanding of the structure‐property relationship and electrocatalytic mechanisms, and their applications in proton exchange membrane fuel cells. Current challenges and future perspectives in this emerging field are also discussed.

Layered catalyst: The attachment of α‐amino acid ligands to inorganic nanosheets for use as ligands to vanadium, resulted in a catalyst that enhanced the enantioselectivity of the epoxidation of allylic alcohols (see picture) . The catalyst can be colloidized, allowing for the catalytic reactions to be carried out under pseudo‐homogeneous reaction conditions and also the catalysts to be directly recycled by simple liquid/liquid separation.

Promotion of heterogeneous asymmetric catalysis is of major interest in the asymmetric catalysis field. In this work, a novel strategy for the synthesis of L-proline-grafted mesoporous silica with alternating hydrophobic and hydrophilic blocks to promote the heterogeneous asymmetric catalysis was reported. The surface synergies in the neat environment and the interface acceleration in aqueous medium thereby fostered high catalytic activities and enantioselectivity in the direct aldol reaction and the Knoevenagel−Michael cascade reaction. The L-proline loading could be reduced to as low as 0.63 mol %, giving 95% ee for anti-isomers and 81% ee for syn-isomers in the catalytic asymmetric aldol reaction of nitrobenzaldehyde and cyclohexanone, which was hard to accomplish on the homogeneous counterpart. In the direct asymmetric aldol reaction of ethyl-2-oxoacetate and cyclohexanone, 82% yield in 24 h and 90% ee were achieved. More exciting, the catalysts were applied to more exigent reactions. As an example, in the Knoevenagel−Michael cascade reaction, 85% yield in 10 h and up to 91% ee was achieved.

Confinement, an effective strategy to improve the enantioselectivity in metal-catalyzed asymmetric synthesis, is a great challenge to the heterogeneous organocatalysis via hydrogen-bonding activation in that hydrogen bonding is more sensitive to the complicated spatial or chemical microenvironment in confined spaces. Here, visible improvement of enantioselectivity has been experimentally achieved on heterogeneous 9-amino (9-deoxy) epiquinine and 9-thiourea epiquinine catalysts in the Michael addition by rationally modulating the pore size of the mesoporous host. The enantiomer excess for heterogeneous 9-thiourea epiquinine is level with the homogeneous counterpart when the support pore size is reduced to an optimized spatial dimension. Theoretical calculations revealed that the immobilization can switch the activation routes, and the hydrogen-bonding interaction between substrate and pore wall influences the energy gap between R/S transition states, well accounting for the dependence of enantioselectivity on the pore size experimentally observed in the heterogeneous organocatalytic Michael addition. The results not only demonstrate significant development in the comprehension of confinement in the heterogeneous asymmetric catalysis but also suggest an original strategy in designing efficient enantioselective heterogeneous catalysts.