Pyrene-Based 2D Covalent Organic Framework Engineered with 3D-MoS2-Nanoflowers Tuned with High Surface Area Assisted in Visible-Light-Driven Photocatalytic H2 Evolution and CO2 Reduction

Covalent organic frameworks (COFs), an emerging category of crystalline and porous substances, have demonstrated exceptional activity in visible-light-mediated H2 evolution in the past few years. However, the utilization of noble metal cocatalysts remains indispensable for achieving a high rate of hydrogen evolution in all COF-based photocatalysts. But, in this study, we introduce a noble-metal-free yet more effective system for COF-based photocatalytic H2 evolution. Herein, we introduce a pyrene-based two-dimensional (2D) covalent organic framework, integrated with three-dimensional (3D) MoS2 nanoflowers to build a 3D–2D heterojunction photocatalyst MoS2@TPPy-COF, utilizing a single-step hydrothermal approach to address those issues. This highly conjugated 3D–2D heterocomposite MoS2@TPPy-COF acquires a band gap of 1.98 eV, demonstrating appealing catalytic efficiency in water splitting as well as CO2 reduction reaction under illumination of visible light. X-ray diffraction (XRD), Fourier-transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–vis), high resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) studies are performed to analyze chemical, structural, morphological, and optical nature. Further electrochemical studies (transient photocurrent response, electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV)) reveal that molybdenum disulfide in this heterocomposite acts as an efficient non-noble metal cocatalyst, which greatly facilitates the migration of photogenerated electrons from COF to MoS2 and significantly improves the segregation of photogenerated e–/h+ pairs, resulting in enhanced activity toward H2 evolution and formic acid formation of the resulting heterocomposite (MoS2@TPPy-COF) compared to pure TPPy-COF (118 μmol g–1). H2 evolution of the MoS2@TPPy-COF heterocomposite is 12,874 μmol g–1 in 10 h, and for HCOOH synthesis, the rate is 966 μmol g–1 in 3 h. This study shows that a successful method for generating highly efficient photocatalysts is the skillful blending of organic moieties (COFs) and inorganic components into an integrated hybrid with a 3D–2D connectivity.