Crystalline and porous covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) materials have attracted enormous attention in the field of photocatalytic H evolution due to their long-range order structures, large surface areas, outstanding visible light absorbance, and tunable band gaps. In this work, we successfully integrated two-dimensional (2D) COF with stable MOF. By covalently anchoring NH -UiO-66 onto the surface of TpPa-1-COF, a new type of MOF/COF hybrid materials with high surface area, porous framework, and high crystallinity was synthesized. The resulting hierarchical porous hybrid materials show efficient photocatalytic H evolution under visible light irradiation. Especially, NH -UiO-66/TpPa-1-COF (4:6) exhibits the maximum photocatalytic H evolution rate of 23.41 mmol g h (with the TOF of 402.36 h ), which is approximately 20 times higher than that of the parent TpPa-1-COF and the best performance photocatalyst for H evolution among various MOF- and COF-based photocatalysts.

Cellulose nanofibrils are biocompatible nanomaterials derived from sustainable natural sources. We report hydrogelation of carboxylated cellulose nanofibrils with divalent or trivalent cations (Ca(2+), Zn(2+), Cu(2+), Al(3+), and Fe(3+)) and subsequent formation of interconnected porous nanofibril networks. The gels were investigated by dynamic viscoelastic measurements. The storage moduli of the gels are strongly related to valency of the metal cations and their binding strength with carboxylate groups on the nanofibrils. Hydrogel moduli may be tuned by appropriate choice of cation. Cation-carboxylate interactions are proposed to initiate gelation by screening of the repulsive charges on the nanofibrils and to dominate gel properties through ionic cross-linking. Binding energies of cations with carboxylate groups were calculated from molecular models developed for nanofibril surfaces to validate the correlation and provide further insight into the cross-linked structures. The cellulose nanofibril-based hydrogels may have a variety of biomedical and other applications, taking advantage of their biocompatibility, high porosity, high surface area, and durability in water and organic solvents.

A double-exchange interaction (DEI) was demonstrated to boost the oxygen evolution reaction (OER) in spinel oxides. DEI was ignited by synergistic actions of constructing nanoheterojunctions and creating oxygen vacancy (V O ) in spinel NiCo 2 O 4 . DEI between octahedrally coordinated Ni and Co resulted in the generation of superior OER active centers Co (3−δ)+ and Ni 3+ . The multiple synergistic effects empower the electrocatalyst with exceptional OER activity, with an overpotential of 270 ± 3 mV at 10 mA/cm 2 and a Tafel slope of 39 mV/dec, both of which are among the best values for NiCo 2 O 4 -based nanostructures, and even better than those for IrO 2 and RuO 2 . Communication pubs.acs.org/JACS

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The conformal deposition of metal nanoparticles (Au, Pd, and Pt) onto natural cellulose fibers using two chemical strategies is reported. The driven mechanism responsible for the high surface coverage of the substrates was identified as the electrostatic interactions between the positively charged cellulose and the either negatively charged nanoparticles or negative metal complex ions. The natural cellulose fibers were rendered cationic by grafting ammonium ions, using an epoxy substitution reaction, to the abundant hydroxyl groups present in cellulose molecules. The first method involved the electrostatic assembly of citrate-stabilized metal nanoparticles directly onto the cationic surfaces of cellulose. The second method involved the adsorption of negative metal complex ions onto the cationic cellulose followed by a reduction reaction. The attained metal nanoparticles bound with cellulose fibers were characterized by electron microscopy (TEM and SEM) and energy-dispersive X-ray spectroscopy (EDX). Both pathways generated metal nanoparticles with high packing densities on the cellulose substrates even when very dilute solutions of metal colloids or metal salts were used. Achieving high surface coverage with low-concentration precursor solutions may open an avenue for the production of flexible catalytic mantles or highly functionalized textile substrates.