COF-5/CoAl-LDH Nanocomposite Heterojunction for Enhanced Visible-Light-Driven CO2 Reduction

Engineered covalent triazine framework inverse opal beads for enhanced photocatalytic carbon dioxide reduction

The development of highly ordered covalent triazine framework (CTF) materials with tailored structures is crucial for advancing functional material applications. Herein, we introduce a novel approach to fabricate covalent triazine framework inverse opal (CTF-IO) photonic crystal beads via a microfluidic-assisted assembly method and pore-confined polymerization. The polymerization process occurs within the interstitial voids of SiO2 nanoparticles (NPs) photonic crystals, where spatial confinement dictates the growth and arrangement of the CTF framework, resulting in a robust and precisely ordered inverse opal (IO) structure. The pore sizes, governed by the packing geometry of SiO2 NPs, are theoretically estimated to highlight the role of confinement in achieving structural fidelity. The unique slow-light effect of the CTF-IO structure enhances light absorption and charge transport, offering a versatile platform for light-driven CO2 conversion applications. As a demonstration, the optimized CTF-240 exhibit superior photocatalytic performance in CO2 reduction, achieving a yield of 118.69μmol g-1h-1 and a selectivity of 97.25 % without sacrificial agents or co-catalysts, significantly outperforming bulk CTF. This work underscores the potential of photonic crystal-guided framework design for diverse advanced applications, providing insights into the interplay between spatial confinement, structural engineering, and functional performance.

In Situ Anchoring of Co Single Atoms within Keto-Enamine COFs via the Coordination of an Interlayer N Atom with Co for the Enhanced Photocatalytic CO2 Reduction Efficiency

Single-atom catalysts (SACs) are prone to agglomeration or migration during catalytic processes, making the development of highly dispersible SACs greatly essential for the performance of photocatalytic CO2 reduction. Herein, cobalt-containing keto-enamine covalent organic frameworks (COFs) (Co/TpPa-1) are successfully in situ synthesized by utilizing the interlayer nitrogen atom coordinated with metallic cobalt, which is used to effectively prevent the agglomeration of monometallic atoms to ensure the homogeneous dispersion of SACs in the resulting metalized COFs. In the photocatalytic CO2 reduction, the Co/TpPa-1 composite exhibits significantly enhanced performance compared to the TpPa-1 COFs. The CO yield of 0.05 mM Co/TpPa-1 composite is approximately 414.5 μmol g-1 h-1, representing a two-order-of-magnitude improvement over the TpPa-1 COF catalyst (approximately 4.15 μmol g-1 h-1). Moreover, the 0.05 mM Co/TpPa-1 composite shows 99.45% selectivity for CO and good stability, maintaining a over 97% CO2 reduction rate after four cycles. The reason lies in the fact that the interaction between monatomic Co and TpPa-1 COFs enhances visible light absorption and extends the lifetime of the photogenerated carriers by promoting electron transfer through the loaded monatomic Co. This work provides a new idea for the catalyst synthesis with high performance and high selectivity.

Brominated metal phthalocyanine-based covalent organic framework for enhanced selective photocatalytic reduction of CO2

Covalent organic frameworks (COFs) have great potential for photocatalytic CO2 reduction, owing to their adjustable structures, porous characteristics, and highly ordered nature. However, poor light absorption, fast recombination of photogenerated electron-hole pairs, and suboptimal coordination conditions have contributed to the hindered efficiency and selectivity observed in photocatalytic CO2 reduction processes. In this work, the integration of bromine (Br) atoms into COFs was achieved through the synthesis process involving nickel (II) tetraaminophthalocyanine (NiTAPc) and 3,6-dibromopyromellitic dianhydride (BPMDA) using a solvothermal approach. The coupling of a porous framework structure alongside the incorporation of Br atoms yields a significant enhancement in photoelectric properties compared to bromine-free COFs. Meanwhile, X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations revealed that the introduction of Br atoms can facilitate the adjustment of the electron configuration around the phthalocyanine unit and diminish the required energy for the photocatalytic reaction. When subjected to visible light irradiation, the NiTAPc-BPMDA COF showcased a CO yield of 148.25 μmol g-1 over a 5-hour period, accompanied by an impressive selectivity of 98%. This work highlights the collaborative influence of phthalocyanines and Br atoms within COF-based photocatalysts, offering an alternative approach for designing and constructing high-performance photocatalysts with elevated yield and selectivity. The synergistic role of phthalocyanines and Br atoms within the COF-based photocatalysts provides an alternative strategy for photocatalysts with high yield and selectivity in the future.

Quantitative Construction of Boronic-Ester Linkages in Covalent Organic Frameworks for the Carbon Dioxide Reduction

Covalent organic frameworks (COFs) have been utilized for catalyzing the reduction of carbon dioxide (CO2RR) due to their atomic metal centers and controllable pore channels, which are facilitated by different covalent bonds. However, the exploration of boron-based linkages in these catalytic COFs has been limited owing to potential instability. Herein, we present the construction of boronic ester-linked COFs through nucleophilic substitution reactions in order to catalyze the CO2 RR. The inclusion of abundant fluorine atoms within the frameworks enhances their hydrophobicity and subsequently improves water tolerance and chemical stability of COFs. The content of boron atoms in the COF linkages was carefully controlled, with COFs featuring a higher density of boron atoms exhibiting increased electronic conductivity, enhanced reductive ability, and stronger binding affinity towards CO2 . Consequently, these COFs demonstrate improved activity and selectivity. The optimized COFs achieve the highest activity, achieving a turnover frequency of 1695.3 h-1 and a CO selectivity of 95.0 % at -0.9 V. Operando synchrotron radiation measurements confirm the stability of Co (II) atoms as catalytically active sites. By successfully constructing boronic ester-linked COFs, we not only address potential instability concerns but also achieve exceptional catalytic performance for CO2 RR.