In Situ Growth of Three-Dimensional MXene/Metal-Organic Framework Composites for High-Performance Supercapacitors

In this study, we propose a versatile method for synthesizing uniform three-dimensional (3D) metal carbides, nitrides, and carbonitrides (MXenes)/metal-organic frameworks (MOFs) composites (Ti₃ C₂ T_X /Cu-BTC, Ti₃ C₂ T_X /Fe,Co-PBA, Ti₃ C₂ T_X /ZIF-8, and Ti₃ C₂ T_X /ZIF-67) that combine the advantages of MOFs and MXenes to enhance stability and improve conductivity. Subsequently, 3D hollow Ti₃ C₂ T_X /ZIF-67/CoV₂ O₆ composites with excellent electron- and ion-transport properties derived from Ti₃ C₂ T_X /ZIF-67 were synthesized. The specific capacitance of the Ti₃ C₂ T_X /ZIF-67/CoV₂ O₆ electrode was 285.5 F g^-1 , which is much higher than that of the ZIF-67 and Ti₃ C₂ T_X /ZIF-67 electrode. This study opens a new avenue for the design and synthesis of MXene/MOF composites and complex hollow structures with tailorable structures and compositions for various applications.

Spherical shape-defined hollow UiO-66 metal-organic frameworks with superior incident photon scattering for enhanced photoelectrochemical H2 evolution

Herein, spherical hollow N-doped carbon-incorporated UiO-66 metal-organic frameworks (MOF, H-UiO-66) are synthesized using bio-inspired polydopamine (pDA) nanoparticles as multifunctional starting templates. The calculated band properties (E_CB = -0.45 eV and E_VB = 2.05 eV versus normal hydrogen electrode (NHE)) strongly reveals the visible light absorption of H-UiO-66 nanostructures thanks to the spherical shape-defined morphology as well as cavity of the hollow structure. The evaluation of photoelectrochemical (PEC) water splitting performance of H-UiO-66 photoanodes shows maximum photocurrent density as 10.95 mA/cm² at 1.53 V versus RHE under LED illumination in which almost no response is recorded at dark. Furthermore, the improved visible-light sensitive PEC water splitting performance of H-UiO-66 photoanodes could be attributed to the main advantages of the one-pot synthesis method of hollow MOFs using multifunctional pDA as follows: i) the hollow morphology provides superior incident photon scattering and multi-reflection of photons inside the MOF cavity; ii) presence of N-doped carbon incorporated morphology facilitates the absorption of water molecules as well as the π-polar interaction between water and carbon; and iii) the reduced bang-gap led to the optical localization of light within H-UiO-66 clusters, suggesting a new generation of heterogeneous well-defined nanostructures for sustainable PEC hydrogen production.