Hexavalent chromium (Cr(VI)) have attracted great considerations due to their high toxicity, teratogenicity, and carcinogenicity. In this study, four Zr-MOFs were synthesized and used to comparative study their catalytic performances of oxalic acid (OA) for Cr(VI) removal. Results showed that the removal efficiency for Cr(VI) was reached 65.91%, 78.64%, 53.58%, and 96.32% by MOF-525, MOF-525(Co), MOF-525(Zn), and MOF-525(Fe) in the presence of OA when the initial Cr(VI) concentration was 100 mg·L⁻¹, respectively. The single-factor experiments for further improving the Cr(VI) removal by MOF-525(Fe)/OA demonstrated that the optimal conditions were OA dosage of 790 mg·L⁻¹, MOF-525(Fe) dosage of 500 mg·L⁻¹ and pH of 2.0, and the MOF-525(Fe)/OA system could be used to treat Cr(VI)-containing wastewater at concentrations below 50 mg·L⁻¹. Ionic strength studies indicated that Na⁺, K⁺, Mg²⁺, Cl⁻ and SO₄²⁻ had little effect on the catalytic reduction of Cr(VI), while high concentrations of Ca²⁺ (0.10 and 0.25 mol·L⁻¹), NO₃⁻ (0.25 mol·L⁻¹), and PO₄³⁻ (0.25 mol·L⁻¹) had significant inhibition effects. The reusability experiments showed that the stability of MOF-525(Fe) was excellent and it could be used for potential applications. Based on the results of Fourier Transform Infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and Electron Paramagnetic Resonance spectrometer (EPR), the possible reduction mechanism of Cr(VI) by MOF-525(Fe)/OA system were proposed as following: The complexation of OA with Fe³⁺ was firstly complexed to produce Fe²⁺ and CO₂•⁻, then Cr(VI) was combined with Zr−O and Fe−O clusters in MOF-525(Fe) to obtain activation energy and the reduction ability was enhanced at the same time, and finally, Cr(VI) obtained electrons from CO₂•⁻ and was sequentially reduced as Cr(V) and Cr(Ⅲ).

Both electron-hole recombination and exogenous regional hypoxia restrict the efficiency of thermoelectriccatalytic therapy. Here, a Pt-TiO2-x/Ti3C2Tx-PEG thermoelectric nanoheterojunction was constructed to facilitatecharge carrier separation and relieve tumor hypoxia. In situ growth of Pt single atoms (SAs) and titaniumoxidewith oxygen vacancy on Ti3C2Tx MXene could not only elevate the charge separation efficiency, but alsohinderthe recombination of thermoelectric-induced positive and negative charges, thus enhancing the reactive oxygenspecies (ROS) generation catalyzed by the thermoelectric effect. The Pt SAs exhibited satisfactory catalase-like(CAT-like) activity, which could catalyze the decomposition of hydrogen peroxide to produce oxygen, alleviatingthe hypoxic tumor microenvironment. Furthermore, the existence of oxygen vacancy titaniumoxide couldalsobeused as a sonosensitizer for sonodynamic therapy, achieving abundant ROS generation cooperatedwiththermoelectric catalytic therapy. Moreover, the photothermal conversion efficiency of Ti3C2Tx MXenewasaugmented by Pt SAs with surface plasmon resonance effect, which was beneficial to achieve enhanced CAT-likeactivity and thermoelectric catalytic therapy. The tumor-specific thermoelectric nanoheterojunction integratesthermoelectric therapy, sonodynamic therapy, and photothermal therapy, demonstrating excellent tumorsuppression efficiency both in vitro and in vivo. Therefore, this study provides a highly feasible and promisinginsight into photo-thermo-electric/US-mediated cancer treatment.

Defects and chemical dopants in metal-free carbon materials critically influence their catalytic performance in the oxygen reduction reaction (ORR). This study investigates the impact of nitrogen, oxygen dopants, and vacancy defects on the ORR activity of monolayer graphene. Our systematic introduction of these elements reveals that while nitrogen doping alone offers limited enhancement, its combination with vacancy defects or oxygen significantly boosts activity—up to 12.8 times compared to pure nitrogen doping and 7.7 times over pristine graphene at 0.4 V vs RHE. The results underscore oxygenated defects as key facilitators of the four-electron pathway, enhancing ORR kinetics more than nitrogen alone. This work highlights the intricate roles of vacancy defects and mixed dopants in optimizing ORR performance in nitrogen-doped graphene, providing insights for the design of efficient metal-free catalysts.

Furthermore, increased defect density correlates positively with improved ORR kinetics, where vacancy defects contribute to enhanced reaction kinetics and water production, while nitrogen dopants primarily affect selectivity towards hydroperoxide via a two-electron pathway. This comprehensive analysis suggests that optimal ORR activity in nitrogen-doped graphene arises from the synergistic interactions among vacancy defects, oxygen, and nitrogen dopants, rather than solely attributing activity to nitrogen species.

Water issues represents one of the biggest challenges of the 21st century. The United Nations
has addressed Sustainable Development Goal (SDG) to answers the water crisis. The increase of
water demand in the different sectors (agriculture, industry and household), and the water stress that
is globally rising in the meantime are responsible for this critical issue. To face it, the water reuse
approach is more and more considered. However, before reusing wastewater there is the need to
completely remove emerging pollutants (e.g., pharmaceuticals, pesticides, personal care products)
since they are not eliminated by the bioprocesses typically applied in plants. Still, wastewater
contains valuable chemicals (e.g., phosphate, magnesium) that could be recovered in the meantime.
Electrochemical systems can tune the removal and recovery steps by playing on the applied
potential/current, in constrats with chemical processes. They also offer the advantages of operating
several unit operations (separation and conversion technologies) without the need for chemicals
addition and within the same reactor design. Moreover, vector of energy could be electrogenerated
(e.g., hydrogen (H2)). This presentation will focus on case studies implementing electroprecipitation, electro-sorption and electro-reduction/-oxidation for resource recovery in wastewater
under microfluidic conditions.