Two complementary design strategies, isomorphous ligand replacement and heterocycle doping, have been applied to iteratively enhance the proton conductivity of a metal-organic framework, β-PCMOF2. The resulting materials, PCMOF2/(Pz) and PCMOF2/(Tz) (Pz = 1H-pyrazole, Tz = 1H-1,2,4-triazole), have their proton conduction raised almost 2 orders of magnitude compared to β-PCMOF2. The bulk conductivities of these materials are over 10 S cm at 85 °C and 90% relative humidity (RH), while maintaining the parent MOF structure. A solid state synthetic route for doping 1-D channels is also presented.

Cyrene, a green bioderived solvent from waste cellulose, was applied into the synthesis of metal–organic frameworks (MOFs). The MOF, HKUST-1, exhibited an even better Brunauer–Emmett–Teller surface area than HKUST-1 synthesized with DMF. Four additional archetypal MOFs were also synthesized to verify the universal application of Cyrene in MOF manufacturing. However, the BET surface areas were lower than DMF-made MOFs. It was observed that an aldol-condensation product of two Cyrene molecules in addition to Cyrene trapped within the pores are responsible for the lower than expected surface area. The use of Cyrene has led to a series of design principles that eliminate the need for problematic solvents such as DMF and can be applied to the synthesis of a wide range of MOFs

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Photocatalytic CO 2 reduction has been known to be one of the most potential technologies for sustaining the development of human society. However, rapid recombination of photoexcited charges in semiconductors often gets in the way of photocatalytic reaction and annoyingly suppresses the photocatalytic performance. Here, amine-modified step-scheme (S-scheme) porous graphite carbon nitride (g-C 3 N 4 )/CdSe−diethylenetriamine (A-PCN/ CdSe−DETA) was fabricated via a simple one-step microwave hydrothermal method. The presence of amine functional groups allows for the uniform dispersion of CdSe−DETA on PCN by acting as an organic linker to anchor CdSe−DETA onto PCN nanosheets and forming a close-contact interface. The successful formation of the S-scheme heterojunction along with the built-in electric field between PCN and CdSe−DETA was substantiated through X-ray photoelectron spectroscopy analysis, radical trapping test, and the density functional theory calculation. Taken together, the modification by amine and formation of the S-scheme heterojunction resulted in the optimized A-PCN/CdSe−DETA composite exhibiting extraordinary photocatalytic CO 2 reduction performance without the use of a sacrificial agent, achieving a CO production rate of 25.87 μmol/(h g) under visible-light irradiation. This work provides insight into the functionalization of S-scheme photocatalysts using amine functional groups, providing enormous opportunities for various applications beyond photocatalysis.

Four new phosphonate MOFs were prepared with cationic dimethylbipiperdinium units: [La2(H2 L)1.5(AcO)2Br·3.25H2O], α-PCMOF-21-Br; [La2(H2 L)1.5(AcO)­Cl2·5.25H2O], α-PCMOF-21-Cl; [La­(H2 L) (AcO)­Br0.5·4.93H2O­(HBr)1.11], β-PCMOF-21-Br; and [La­(H2 L) (AcO)0.5Cl·5.42H2O­(HCl)1.79], β-PCMOF-21-Cl. All frameworks have the same La phosphonate network structure but differ in the secondary anions (acetate, bromide, chloride), both coordinated and free. All frameworks showed the ability to dehydrate reversibly. Different phases result from very subtle differences in preparation; specifically, the degree of hydration of the ligand impacts the product phase even though syntheses are carried out in water. The alpha phases show a flexible structure by powder X-ray diffraction. The beta phases contain a reproducible stoichiometry of free ligands in the pores that both locks and partially fills the open structure. Alternating current impedance analysis was performed to study proton conductivity. All compounds, except for β-PCMOF-21-Cl, conduct better than 10–3 S cm–1 at 85 °C and 95% RH. The trends show that the alpha phases conduct better than the partially pore-blocked beta phases and also that the bromide structures conduct better than the chlorides. To further study the role of the anion, 35Cl and 81Br solid-state NMR was performed to elucidate dynamics. These studies also showed the ability of anions to be volatilized from the pores, and TGA–MS confirmed the loss of HX species. Impedance analysis showed a clear decrease in proton conductivity after the loss of the halides, more pronounced in the bromide-containing structures.