Recently, metal-organic framework (MOF)-based multienzyme systems integrating different functional natural enzymes and/or nanomaterial-based artificial enzymes are attracting increasing attention due to their high catalytic efficiency and promising application in sensing. Simple and controllable integration of enzymes or nanozymes within MOFs is crucial for achieving efficient cascade catalysis and high stability. Here, we report a facile electrochemical assisted biomimetic mineralization strategy to prepare an artificial multienzyme system for efficient electrochemical detection of biomolecules. By using the GOx@Cu-MOF/copper foam (GOx@Cu-MOF/CF) architecture as a proof of concept, efficient enzyme immobilization and cascade catalysis were achieved by in situ encapsulation of glucose oxidase (GOx) within MOFs layer grown on three-dimensional (3D) porous conducting CF via a facile one-step electrochemical assisted biomimetic mineralization strategy. Due to the bio-electrocatalytic cascade reaction mechanism, this well-designed GOx@Cu-MOF modified electrode exhibited superior catalytic activity and thermal stability for glucose sensing. Notably, the activity of GOx@Cu-MOF/CF still remained at ca. 80% after being incubated at 80 ℃. In sharp contrast, the activity of the unprotected electrode was reduced to the original 10% after the same treatment. The design strategy presented here may be useful in fabricating highly stable enzyme@MOF composites applied for efficient photothermal therapy and other platform under high temperature.

The high cost and poor durability of Pt nanoparticles (NPs) have always been great challenges to the commercialization of proton exchange membrane fuel cells (PEMFCs). Pt-based intermetallic NPs with a highly ordered structure are considered as promising catalysts for PEMFCs due to their high catalytic activity and stability. Here, we reported a facile method to synthesize N-doped carbon encapsulated PtZn intermetallic (PtZn@NC) NPs via the pyrolysis of Pt@Zn-based zeolitic imidazolate framework-8 (Pt@ZIF-8) composites. The catalyst obtained at 800 ℃ (10%-PtZn@NC-800) was found to exhibit a half-wave potential (E_1/2) up to 0.912 V versus reversible hydrogen electrode (RHE) for the cathodic oxygen reduction reaction in an acidic medium, which shifted by 26 mV positively compared to the benchmark Pt/C catalyst. Besides, the mass activity and specific activity of 10%-PtZn@NC-800 at 0.9 V versus RHE were nearly 3 and 5 times as great as that of commercial Pt/C, respectively. It is worth noting that the PtZn@NC showed excellent stability in oxygen reduction reaction (ORR) with just 1 mV of the E_1/2 loss after 5, 000 cycles, which is superior to that of most reported PtM catalysts (especially those disordered solid solutions). Furthermore, such N-doped carbon shell encapsulated PtZn intermetallic NPs showed significantly enhanced performances towards the anodic oxidation reaction of organic small molecules (such as methanol and formic acid). The synergistic effects of the N doped carbon encapsulation structure and intermetallic NPs are responsible for outstanding performances of the catalysts. This work provides us a new engineering strategy to acquire highly active and stable multifunctional catalysts for PEMFCs.

Researchers appear to have neglected a special form of crystallites, pentagonal cyclic twinning, in which an obvious two-dimensional lattice expansion exists leading to novel physical–chemical properties associated with the changes in geometric and electronic structures. Using the storage and release of hydrogen in Pd nanocrystals as a probe, we have found that icosahedral pentagonal cyclic twinned Pd nanocrystals had distinct hydrogen storage properties, due to the two-dimensional lattice expansions, quite different from those of the octahedral single crystalline counterpart. In addition, the two-dimensional lattice expansion in pentagonal cyclic twinned Pd nanocrystals causes a change in electronic structure, which results in novel catalytic properties involving in situ formation of PdH_x pentagonal cyclic twinned nanocrystals.

Rational synthesis of bimetallic alloy nanocrystals (NCs) is still a great challenge. Especially, spatially uniform alloy NCs are very difficult to achieve because of the different reduction rates of the individual alloy components. Herein we propose a facile wet chemical synthetic strategy to prepare uniform bimetallic alloy NCs with tunable composition by controlling the growth of alloy NCs under diffusion controlled conditions. Using this strategy, we successfully synthesized trisoctahedral (TOH) Au–Pd alloy NCs enclosed by {hhl} high-index facets with uniform spatial distributions and different compositions. Significantly, using our strategy, the composition of the as-prepared Au–Pd alloy NCs is identical to the ratio of the two metal precursors in the reaction solution over a wide range. Investigation of the composition-dependent electrochemical behavior of the as-prepared TOH Au–Pd alloy NCs showed that the TOH Au–Pd alloy NCs containing 14.1 atom% Pd exhibited the best activity.