Photocatalytic water splitting using sunlight is a promising technology capable of providing high energy yield without pollutant byproducts. Herein, we review various aspects of this technology including chemical reactions, physiochemical conditions and photocatalyst types such as metal oxides, sulfides, nitrides, nanocomposites, and doped materials followed by recent advances in computational modeling of photoactive materials. As the best-known catalyst for photocatalytic hydrogen and oxygen evolution, TiO 2 is discussed in a separate section, along with its challenges such as the wide band gap, large overpotential for hydrogen evolution, and rapid recombination of produced electron-hole pairs. Various approaches are addressed to overcome these shortcomings, such as doping with different elements, heterojunction catalysts, noble metal deposition, and surface modification. Development of a photocatalytic corrosion resistant, visible light absorbing, defect-tuned material with small particle size is the key to complete the sunlight to hydrogen cycle efficiently. Computational studies have opened new avenues to understand and predict the electronic density of states and band structure of advanced materials and could pave the way for the rational design of efficient photocatalysts for water splitting. Future directions are focused on developing innovative junction architectures, novel synthesis methods and optimizing the existing active materials to enhance charge transfer, visible light absorption, reducing the gas evolution overpotential and maintaining chemical and physical stability.

Using molecular simulation for adsorbent screening is computationally expensive and thus prohibitive to materials discovery. Machine learning (ML) algorithms trained on fundamental material properties can potentially provide quick and accurate methods for screening purposes. Prior efforts have focused on structural descriptors for use with ML. In this work, the use of chemical descriptors, in addition to structural descriptors, was introduced for adsorption analysis. Evaluation of structural and chemical descriptors coupled with various ML algorithms, including decision tree, Poisson regression, support vector machine and random forest, were carried out to predict methane uptake on hypothetical metal organic frameworks. To highlight their predictive capabilities, ML models were trained on 8% of a data set consisting of 130,398 MOFs and then tested on the remaining 92% to predict methane adsorption capacities. When structural and chemical descriptors were jointly used as ML input, the random forest model with 10-fold cross validation proved to be superior to the other ML approaches, with an R of 0.98 and a mean absolute percent error of about 7%. The training and prediction using the random forest algorithm for adsorption capacity estimation of all 130,398 MOFs took approximately 2 h on a single personal computer, several orders of magnitude faster than actual molecular simulations on high-performance computing clusters.

A recent report from the United Nations has warned about the excessive CO2 emissions and the necessity of making efforts to keep the increase in global temperature below 2 °C. Current CO2 capture technologies are inadequate for reaching that goal, and effective mitigation strategies must be pursued. In this work, we summarize trends in materials development for CO2 adsorption with focus on recent studies. We put adsorbent materials into four main groups: (I) carbon-based materials, (II) silica/alumina/zeolites, (III) porous crystalline solids, and (IV) metal oxides. Trends in computational investigations along with experimental findings are covered to find promising candidates in light of practical challenges imposed by process economics.

Magnetic behavior of nanostructured mesoporous manganese oxide materials, designated UCT-1 and UCT-18, were studied using a combination of superconducting quantum interference device (SQUID) magnetometry and 55 Mn zero-field spin−echo nuclear magnetic resonance (NMR). Curie−Weiss fits to the magnetic susceptibility for the UCT-1 and UCT-18 samples calcined at 550 °C yielded paramagnetic moment values consistent with spin-only Mn 3+ ions in the α-Mn 2 O 3 phase (S = 2, 4.90 μ B ). However, the magnetization and NMR results reported here clearly identify a small amount of the Mn 3 O 4 second phase (ferrimagnetic with T C ≈ 43 K) that does not appear in X-ray diffraction (XRD). The study resulted in the observation of fascinating magnetic behavior:(1) exchange bias, which occurs in cases where a ferromagnetic (or ferrimagnetic) phase forms a boundary with an antiferromagnetic phase and (2) a magnetic contribution attributed to uncompensated spins on the surfaces of the α-Mn 2 O 3 nanoparticles. The presence of Mn 3 O 4 and the interplay of Mn 3+ and Mn 2+ impact the catalytic properties.

We report microwave assisted synthesis of a series of highly hydrophobic porous organic polymers of poly divinylbenzene (PDVB), for the first time, which were modified by amine-rich co-monomers of vinyl imidazole (VI) and vinyl triazole (VT) resulting in PDVB-VI and PDVB-VT adsorbents. There is an optimum amount of incorporated co-monomer and initiator which led to high adsorptive activity of the material towards CO2. Atmospheric CO2 adsorption was enhanced by the addition of amine moieties while maintaining an optimum surface area and pore volume. A certain amount of initiator led to better incorporation of VT monomer while surface area and pores remain accessible. A maximum CO2 adsorption of 2.65 mmolg-1 at 273 K/1 bar was achieved for triazole based adsorbent (PDVB-VT) with 0.7 g of VT and 0.07 g of initiator. In comparison with a non-functionalized material (PDVB) with 1.2 mmolg-1 CO2 uptake, the adsorption efficiency was enhanced more than twice. The adsorbent maintained its efficiency up to seven cycles. Theoretical modeling confirms the active site is nitrogen on the imidazole/ triazole ring and that incorporation of VT to the polymeric networks enhanced the adsorptive properties better than vinyl imidazole (VI) due to more active sites.While absorption by amine-solution has drawbacks of corrosion, considerable energy loss, and inefficient regeneration, this has been the most widely adopted strategy [9]. Adsorption by solids provides some Porous polymers provide several advantages of (i) clear design of the high surface area and well-defined porosity, (ii) easy processing, (iii)and light elemental composition which provide weight advantages [53]. Recently, several porous polymers (mesoporous or microporous) have been developed for CO 2 capture [54,55]. Amine modified porous polymers have also been drawn up to adsorb CO 2 more