Defective or heteroatom-doped metal-free carbon materials (MFCMs) have been regarded as efficient oxygen reduction reaction (ORR) catalysts in the past decade. However, the active centers for ORR in MFCMs are hard to confirm precisely and synthesize controllably through common methods such as high-temperature pyrolysis or heteroatom doping. To verify the precise structure acting as the active center for the ORR, we first report two crystalline metal-free thiophene-sulfur covalent organic frameworks (MFTS-COFs) as ORR catalysts. The MFTS-COFs show more positive catalytic capability than the thiophenefree COF, indicating that pentacyclic thiophene-sulfur building blocks act as active centers to induce ORR catalytic activity. MFTS-COFs with higher contents of thiophene-sulfur exhibit better ORR performance. The experimental identification is supported by density functional theory calculations. These results thus demonstrate that rational design and precise synthesis of metal-free crystalline organic materials can promote the development of new ORR catalysts.

The functionalization of three-dimensional (3D) covalent organic frameworks (COFs) is essential to broaden their applications. However, the introduction of organic groups with electroactive abilities into 3D COFs is still very limited. Herein we report the first case of 3D tetrathiafulvalene-based COFs (3D-TTF-COFs) with non- or 2-fold interpenetrated pts topology and tunable electrochemical activity. The obtained COFs show high crystallinity, permanent porosity, and large specific surface area (up to 3000 m2/g). Furthermore, these TTF-based COFs are redox active to form organic salts that exhibit tunable electric conductivity (as high as 1.4 × 10–2 S cm–1 at 120 °C) by iodine doping. These results open a way toward designing 3D electroactive COF materials and promote their applications in molecular electronics and energy storage.

Three-dimensional (3D) covalent organic frameworks (COFs) are excellent porous crystalline polymers for numerous applications, but their building units and topological nets have been limited. Herein we report the first 3D large-pore COF with stp topology constructed with a 6-connected triptycene-based monomer. The new COF (termed JUC-564) has high surface area (up to 3300 m 2 g -1 ), the largest pore (43 Å) among 3D COFs, and record-breaking low density in crystalline materials (0.108 g cm -3 ). The large pore size of JUC-564 is confirmed by the incorporation of a large protein. This study expands the structural varieties of 3D COFs as well as their applications for adsorption and separation of large biological molecules. Supporting InformationMethods and synthetic procedures, SEM, FTIR, solid state 13 C NMR, TGA, BET plot, and unit cell parameters. This material is available free of charge via the internet at http://pubs.acs.org.

The growth of three-dimensional covalent organic COFs from high-connectivity building blocks and facilitates their future applications in energy storage and environment protection. Supporting Information Methods and synthetic procedures, SEM, FTIR, solid state 13 C NMR, TGA, BET plot, and unit cell parameters. This material is available free of charge via the internet at http://pubs.acs.org.

No abstract

No abstract

As an alternative to TiO2 photocatalysts, ZnO exhibits a large potential for photocatalytic (PC) applications in environmental treatments, such as degradation of wastewater, sterilization of drinking water, and air cleaning. However, the efficiency achieved with ZnO to date is far from that expected for commercialization, due to rapid charge recombination, photo-corrosion as well as poor utilization of solar energy. Fortunately, in recent years, a great number of breakthroughs have been achieved in PC performance (including activity and stability) of micro-/nano- structured ZnO by forming heterojunctions (HJs) with metal nanoparticles (NPs), carbon nanostructures and other semiconductors. In most cases, the improvement of PC performance was ascribed to the better charge separation at the interfaces between ZnO and the other components. Sometimes, the formation of hybrids is also in favor of visible light harvesting. This review summarizes recent advances in the fields of environmental photocatalysis by ZnO based HJs, and especially emphasizes their abilities in degradation of organic pollutants or harmful substances in water. We aim to reveal the mechanism underlying the enhanced PC performance by constructing HJs, and extend the potential of ZnO HJ photocatalysts for future trends, and practical, large-scale applications in environment-related fields.

The layered titanium oxide is a useful and unique precursor for the facile and rapid preparation of the peroxide layered titanium oxide H1.07Ti1.73O4·nH2O (HTO) crystal with enhanced visible light photoactivity. The H2O2 molecules as peroxide chemicals rapidly enter into the interlayers of HTO crystal, and coordinate with Ti within TiO6 octahedron to form a mass of Ti-O-O coordination bond in the interlayers. The introduction of these Ti-O-O coordination bonds result in lowering the band gap of HTO, and promoting the separation efficiency of the photo induced electron–hole pairs. Meanwhile, the photocatalytic investigation indicates that such peroxide HTO crystal has the enhanced photocatalytic performance for RhB degradation and water splitting to generate oxygen under visible light irradiating.