Carbon dioxide (CO 2 ) hydrogenation to methanol with H 2 produced with renewable energy represents a promising path for the effective utilization of a major anthropogenic greenhouse gas, in which catalysts play a key role for CO 2 conversion and methanol selectivity. Although still under development, indium oxide (In 2 O 3 )-based catalysts have attracted great attention in recent years due to the excellent selectivity to methanol along with high activity for CO 2 conversion. In this review, we discuss recent advances of In 2 O 3 -based catalysts for CO 2 hydrogenation based on both experimental and computational studies. Various strategies have been adopted to improve the catalytic performance by facilitating the formation of surface oxygen vacancies (In 2 O 3−x ) as active sites, the activation of CO 2 and H 2 toward hydrogenation to methanol to mitigate reverse water−gas shift reaction, and the stabilization of the key intermediates. Mechanistic insights are gained from combining catalytic kinetic studies, in situ characterization, and theoretical investigations involving CO 2 conversion via the formate HCOO* pathway versus the carboxyl COOH* pathway. Strategies to further promote selective CO 2 hydrogenation to methanol include adding a metal component such as Pd or Ni on In 2 O 3 (which may also involve formation of bimetallic In−M catalysts) to promote H 2 activation and oxygen vacancy formation, combining In 2 O 3 with an oxide promoter such as ZrO 2 to enhance CO 2 adsorption and activation, controlling the concentration of CO and H 2 O to enhance methanol formation, and adopting a second catalytic component to enhance CO 2 conversion to other desired products such as olefins or aromatics on an acid catalyst such as zeolites. Through a comprehensive overview of the recent advances in In 2 O 3related catalysts, the present review paves the way for future development in In 2 O 3 -based selective catalysts for CO 2 hydrogenation to methanol.

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We present here a simple solvothermal method to fabricate metal-organic framework NH2-MIL-53(Al) crystals with controllable size and morphology just by altering the ratio of water in the DMF-water mixed solvent system without the addition of any surfactants or capping agents. With increasing the volume ratio of water in the mixed solvents, a series of NH2-MIL-53(Al) crystals with different sizes and morphologies were synthesized. The average size of the smallest crystal is 76 ± 20 nm, which provides us a simple and environmentally friendly way to prepare nanoscale MOFs. The largest BET surface area of these samples is 1882 m(2) g(-1) that is mainly contributed by its micropore surface area, and its corresponding micropore volume is 0.83 cm(3) g(-1), which have greatly extended its application in the fields of gas adsorption and postsynthetic modification. All these samples were characterized by SEM, XRD, N2 adsorption/desorption, TGA and FT-IR. Then a mechanism for the impact of the water ratio on the crystal size and morphology is presented and discussed.

The MOF material NH 2 -MIL-125(Ti) was synthesized through the solvothermal method, and the morphology can be controlled by simply modulating the concentration of the reactants during crystallization, which ranges from circular plate through tetragon to octahedron. All samples were characterized by SEM, XRD, FT-IR, UV Raman spectra, TGA, Ar adsorption/desorption and UV-vis spectra.In situ XRD results show that this Ti-incorporated MOF is highly thermostable until 290 °C. It is interesting to find that the light response of NH 2 -MIL-125(Ti) crystals is closely related to their morphology, and the absorption edges of different morphologies range from 480 nm to 533 nm with band gaps of 2.6 to 2.3 eV, making them potential candidates for photocatalytic applications.

A simple strategy involving desilication and recrystallization of silicalite-1 in tetrapropylammonium hydroxide (TPAOH) solution was successfully developed to prepare hollow zeolite nanocubes and three-dimensionally macroporous zeolite monoliths. Large voids were introduced to silicalite-1 crystals by controlled silicon leaching with OH– and thin intact shells were formed by the recrystallization of silicon with TPA+. The size of nanocubes could be easily controlled from ∼150 nm to ∼600 nm by simply adjusting the size of parent silicalite-1. Apart from template function to increase the yield of hollow silicalite-1, TPA+ adsorbed on the zeolite protects the parent crystal surface where the recrystallization occurred. The size of the mesopores and/or macropores in the hollow zeolite shell can be controlled by varying the amount of competitive Na+ adsorbent added to the TPAOH solution. Furthermore, three-dimensional macroporous zeolite monoliths can be formed when an electrolyte, such as NaCl, was added to the TPAOH solution. When the sample was used as the support for iron-based catalyst for hydrogenation of CO2 to hydrocarbons, both the conversion of CO2 and the selectivity of C5 + higher hydrocarbons were improved.