Yunnan Normal University

Covalent organic frameworks (COFs) with tunable nanochannels and high charge density have shown great potential for constructing ion-selective membranes. However, COF membranes are limited by their mechanical brittleness and complex fabrication processes in large-scale applications. To address these limitations, we introduced highly ion-selective membranes composed of COFs and cellulose nanofibers (CNFs) for osmotic energy conversion. The COF/CNF nanofluidic membranes (CCNMs) were obtained by vacuum-assisted filtration of COF/CNF suspensions, where ionic COFs providing ion-selective channels were combined with high-strength CNFs through strong hydrogen bonding interactions. Consequently, the CCNMs achieved high ion selectivity (t₊ = 0.97) and power density (5.25 W m^-2) under a 50-fold NaCl gradient, meeting the commercial benchmark for osmotic energy conversion (5 W m^-2). Furthermore, the CCNMs exhibited stable open-circuit voltage (V_OC), short-circuit current (I_SC), and power density during continuous testing for 120 days, suggesting their excellent long-term stability. When used for harvesting osmotic energy between natural river water and seawater, as well as between natural river water and high-salinity lake water, power density values reached 5.24 and 12.47 W m^-2, respectively, highlighting the significant potential of CCNMs as robust and high-performance nanofluidic generators for osmotic power.

Anion exchange membrane water electrolysis faces significant challenges due to the kinetically sluggish four-electron oxygen evolution reaction (OER). Layered double hydroxides (LDHs) are active for OER, however, the fundamental relationship between their electronic structure and catalytic performance remains ambiguous. This work investigates the electronic modulation of Ni sites in NiAl-LDH through strategic incorporation of s-block and d-block metal cations. A distinct volcano-shaped thermodynamic correlation emerges between the Ni valence states and OER activity upon metal substitution. Synergistic modification with Co and Fe (CoFeNiAl-LDH) optimally regulates the Ni d-band center position and oxidation states, which facilitates OH^- adsorption/desorption processes at the electrocatalyst-electrolyte interface, and lowers the energy barrier for the rate-determining *O → *OOH transition. When integrated CoFeNiAl-LDH in an anion exchange membrane electrolyzer, it enables stable water splitting at 100 mA cm^-2 with a low cell voltage of 1.68 V. This work establishes a cation engineering paradigm for rational design of high-efficiency electrocatalysts through precise electronic structure manipulation.

Thermodynamically driven biosynthesis of D-tagatose attracts increasing attention because it overcomes the reaction equilibrium caused by aldose isomerization or ketose epimerization. Specific aldose reductase and D-galactitol 2-dehydrogenase may drive the conversion of D-galactose to D-tagatose through galactitol as the intermediate. In this study, a novel D-galactitol 2-dehydrogenase was identified from a Rhizobiaceae bacterium with the NCBI accession No. of MDF1774848. The enzyme was expressed in His-tagged form and purified by one-step nickel-affinity chromatography. The recombinant enzyme showed the highest activity at pH 9.5 and 30 °C. It showed galactitol as the optimal substrate and D-sorbitol as the second substate. It's in vivo D-tagatose production ability was verified in a metabolically engineered Escherichia coli strain. Using a previously constructed galactitol-producing strain as a chassis microbe, genomic integration of this D-galactitol 2-dehydrogenase gene resulted in the efficient production of D-tagatose with a titer of 1.85 g/L.