No abstract

Covalent organic frameworks have recently shown high potential for photocatalytic hydrogen production. However, their structure-property-activity relationship has not been sufficiently explored to identify a research direction for structural design. Herein, we report the design and synthesis of four benzotrithiophene (BTT)-based covalent organic frameworks (COFs) with different conjugations of building units, and their photocatalytic activity for hydrogen production. All four BTT-COFs had slipped parallel stacking patterns with high crystallinity and specific surface areas. The change in the degree of conjugation was found to rationally tune the rate of photocatalytic hydrogen evolution. Based on the experimental and calculation results, the tunable photocatalytic performance could be mainly attributed to the electron affinity and charge trapping of the electron accepting units. This study provides important insights for designing covalent organic frameworks for efficient photocatalysts.

The development of high‐performance hole transport layer (HTL)‐free perovskite solar cells (PSCs) with a simplified device structure has been a major goal in the commercialization of PSCs due to the economic advantage of low manufacturing cost. Unfortunately, low bandgap (Eg) mixed Pb–Sn perovskites, which have promising utility for constructing efficient all‐perovskite tandem solar cells, have rarely been explored in simplified HTL‐free device configurations. In this study, efficient band bending and defect engineering at the interface between perovskite and indium tin oxide (ITO) are realized via a binary additive system using copper thiocyanate (CuSCN) and glycine hydrochloride (GlyHCl). Using mixed Pb–Sn perovskites decorated with crystalline p‐type CuSCN, the energy level alignment at the hole extractive interface is modulated in favor of hole extraction, simultaneously increasing hole mobility. Suppressed nonradiative carrier recombination in the perovskite bulk, or across the charge extractive interface, is further achieved by GlyHCl without disturbing the efficient hole transfer characteristics. Notably, a more optimized band alignment is achieved at the hole extractive interface with the addition of GlyHCl. The HTL‐free mixed Pb–Sn PSC shows an efficiency up to 20.1% under forward bias with negligible hysteresis, comparable to state‐of‐the‐art high‐performance full‐structured mixed Pb–Sn PSCs.

Developing new linkage-based covalent organic frameworks (COFs) is one of the major topics in reticular chemistry.E lectrically conductive COFs have enabled applications in energy storage and electrochemical catalysis,w hich are not feasible using insulating COFs.D espite significant advances,t he construction of chemically stable conductive COFs by the formation of new linkages remains relatively unexplored and challenging. Here we report the solvent-and catalyst-free synthesis of at wo-dimensional aza-bridged bis(phenanthroline) macrocycle-linked COF (ABBPM-COF) from the thermally induced poly-condensation of at ri-topic monomer and ammonia gas.The ABBPM-COF structure was elucidated using multiple techniques,i ncluding X-rayd iffraction analysis combined with structural simulation, revealing its crystalline nature with an ABC stackingmode.Further experiments demonstrated its excellent chemical stability in acid/base solutions.E lectrical-conductivity measurements showed that the insulating ABBPM-COF becomes as emiconducting material after exposure to iodine vapor.

Developing a stable and highly efficient electrocatalyst for oxygen evolution reactions (OERs) is critical for renewable, safe, and emission-free energy technologies. Perovskite oxides with flexible and tunable electronic structures as...