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The practical applicability of thiolated metal–organic frameworks (MOFs) remains challenging due to their low crystallinity and transient stability. Herein, we present a one-pot solvothermal synthesis process using varying ratios of 2,5-dimercaptoterephthalic acid (DMBD) and 1,4-benzene dicarboxylic acid (100/0, 75/25, 50/50, 25/75, and 0/100) to prepare stable mixed-linker UiO-66-(SH)2 MOFs (ML-U66SX). For each variant, the effects of different linker ratios on the crystallinity, defectiveness, porosity, and particle size have been discussed in detail. In addition, the impact of modulator concentration on these features has also been described. The stability of ML-U66SX MOFs was investigated under reductive and oxidative chemical conditions. The mixed-linker MOFs were used as sacrificial catalyst supports to highlight the interplay of template stability on the rate of the gold-catalyzed 4-nitrophenol hydrogenation reaction. The release of catalytically active gold nanoclusters originating from the framework collapse decreased with the controlled DMBD proportion, resulting in a 59% drop in the normalized rate constants (9.11–3.73 s–1 mg–1). In addition, post-synthetic oxidation (PSO) was used to further probe the stability of the mixed-linker thiol MOFs under harsh oxidative conditions. Following oxidation, the UiO-66-(SH)2 MOF underwent immediate structural breakdown, unlike other mixed-linker variants. Along with crystallinity, the microporous surface area of the post-synthetically oxidized UiO-66-(SH)2 MOF could be increased from 0 to 739 m2 g–1. Thus, the present study delineates a mixed-linker strategy to stabilize the UiO-66-(SH)2 MOF under harsh chemical conditions through meticulous thiol decoration.

Porous functional materials are highly useful as catalysts, adsorbents, and drug-delivery vehicles. The impact of varying the mole ratio of the organic ligand (BTC, trimesic acid) to iron nitrate on the porosity, surface chemistry, and proton conductivity of Fe 2 O 3 -BTC hybrid nanostructures was thoroughly examined. Variation in the BTC content alters the porosity as well as proton conductivity of the hybrid nanoparticles. The improved accessibility of pores and surface area along with functionalization of the surface by trimesic acid was found to be responsible for enhanced and selective dye adsorption. The adsorption capacity of the best Fe 2 O 3 -BTC hybrid nanomaterial was 200 mg g −1 . The Fe 2 O 3 -BTC hybrid nanomaterial provides pH/adsorbent surface charge-dependent selectivity in the adsorption of positive (e.g., methylene blue) and negative dye (fluorescein) from the aqueous solution of their mixture. In addition, the functionalization of pores in the hybrid nanomaterial provides wettability to the pore channels, which allows the protons to conduct through H-bonded water molecules. As a result, the hybrid nanomaterial exhibits enhanced proton conductivity and electrochemical hydrogen evolution reaction. These findings could be useful to develop similar metal oxide−organic hybrid nanoparticles as better adsorbents and electrocatalysts in comparison to the conventional counterparts (i.e., metal oxide or metal−organic frameworks).

Palladium (Pd) has recently emerged as a stable and active yet cheaper alternative electrocatalyst to costly platinum for the formic acid oxidation reaction (FAOR). Crystal engineering, wherein particle morphologies, defects, and facets are selectively altered, can enhance the electrocatalytic activities of Pd nanostructures. Herein, we have demonstrated that a combination of crystal engineering and supporting the nanostructures on a conductive catalyst support (few-layered graphene (FLG)) leads to highly enhanced catalytic activities. FLG was prepared by using liquid-phase exfoliation in aqueous solution of a surfactant. Swollen liquid crystals promoted the nanostructuring of Pd as well as nanocomposite formation as they acted as “soft” templates. Spherical nanoparticles (Pd0D), nanowires (Pd1D), and nanosheets (Pd2D) of Pd were formed and preferentially deposited on graphene sheets on the exposure of mesophases containing graphene along with Pd2(dba)3 to hydrazine vapor, H2, and CO, respectively. The Pd1D/FLG nanocomposite exhibited an exceptional electrocatalytic activity for FAOR. It had many folds higher electrocatalytically active surface area (ECSA), current density, and stability than the other nanocomposites as well as other Pd-based catalysts reported in the literature. Increased presence of more active Pd(100) facets was identified as the major reason for the enhanced catalytic activity of Pd1D. Supporting the Pd nanostructures on graphene led to enhanced electrocatalytic activities owing to the preserved surface sites of Pd nanoparticles, enhancement in electronic conductivities, and mass transfer and charge transfer from graphene to Pd.

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