Pt-coated Ni layer supported on Ni foam catalyst (denoted PtNi/Nifoam) was investigated for the oxidation of the formic acid (FAO) in acidic media. The prepared PtNi/Ni foam catalyst was studied as a function of the formic acid (FA) concentration at bare Pt and PtNi/Nifoam catalysts. The catalytic activity of the PtNi/Nifoam catalysts, studied on the basis of the ratio of the direct and indirect current peaks (jd)/(jnd) for the FAO reaction, showed values about 10 times higher compared to those on bare Pt, particularly at a low formic acid concentrations, reflecting the superiority of the former catalysts for the oxidation of FA to CO2. Ni foams provide a large surface area for the FOR while synergistic effects between Pt nanoparticles and Ni-oxy species layer on Ni foams contribute significantly to the enhanced oxidation of FA via the direct pathway, making it almost equal to the indirect pathway, particularly at low formic acid concentrations.

Metal organic frameworks (MOFs) are used in catalysis due to their high specific surface area and porous structure. The dispersed active sites and limited reaction space render MOFs have the potential for highly selective electrocatalytic CO2 reduction reaction (ECO2RR). Meanwhile, formic acid (HCOOH) is attracting attention as a liquid product with high economic benefits. This review summarizes the MOFs and their derivatives applied for ECO2RR into HCOOH products. The preparation methods of MOFs as electrocatalysts and their unique advantages are discussed. A series of MOFs, and MOFs derivatives obtained by electrochemical reduction or carbonization processes are highlighted, including metal nanomaterials, carbon-based nanocomposites, single-atom catalysts, and bimetallic nanocomposites. Depending on the MOFs building units (metal ions and organic linkers) and the reaction conditions of derivatization, MOFs-based catalysts exhibit rich diversity and controllable modulation of catalytic performance. Finally, the challenges encountered at this stage and the future research directions of MOFs-based catalysts are proposed.

Electrocatalytic reduction of CO2 to valuable chemicals can alleviate the energy crisis, and solve the greenhouse effect. The key is to develop non-noble metal electrocatalysts with high activity, selectivity and stability. Herein, bimetallic MOF materials (BiZn-MOF, BiSn-MOF and BiIn-MOF) were constructed by coordinating the P-zone transition metals Zn, In, Sn and Bi with the organic ligand 3-amino-1H-1,2,4-triazole-5-carboxylic acid (H2atzc) through a rapid microwave synthesis approach. The coordination centers in bimetallic MOF Catalyst were regulated to optimize the catalytic performance to CO2RR. The optimized catalyst BiZn-MOF exhibited high catalytic activity than those of Bi-MOF, BiSn-MOF and BiIn-MOF. The BiZn-MOF exhibited a higher selectivity for formate production with a Faradic efficiency (FE=92%) at a potential of -0.9 V (vs. RHE) with a current density of 13 mA/cm2. The current density maintained for 13 h continuous electrolysis. The electrochemical conversion of CO2 to formic acid mainly follows the *OCHO pathway. The good catalytic performance of BiZn-MOF may be attributed to the Bi-Zn bimetallic coordination centers in the MOF, which can reduce the binding energies of the reaction intermediates by tuning the electronic structure and atomic arrangement. This study provides a feasible strategy for performance optimization of bismuth-based catalysts.

The present review revisits representative studies addressed to develop efficient carbon-based heterogeneous catalysts for two important reactions, namely, the production of hydrogen from formic acid and the hydrogenation of carbon dioxide to formic acid. The HCOOH-CO2 system is considered a promising couple for a hydrogen storage system that would be involved in an ideal carbon-neutral cycle. Significant advancements have been achieved in those catalysts designed to catalyze the dehydrogenation of formic acid under mild reaction conditions, while much effort is still needed to catalyze the challenging CO2 hydrogenation reaction. The design of carbon-based heterogeneous catalysts for these reactions encompasses both the modulation of the properties of the active phase (particle size, composition, and electronic properties), as well as the modification of the supports by means of incorporation of nitrogen functional groups. These approaches are herein summarized to provide a compilation of the strategies followed in recent studies to set the basis for a hydrogen storage system attained by the HCOOH-CO2 couple.

Lignocellulosic biomass fractionation is typically performed using methods that are somehow harsh to the environment, such as in the case of the kraft pulping. In recent years, the development of new sustainable and environmentally friendly alternatives has grown significantly. Among the developed systems, bio-based solvents emerge as promising alternatives for biomass processing. Therefore, in the present work, the bio-based and renewable chemicals, levulinic acid (LA) and formic acid (FA), were combined to fractionate lignocellulosic waste (i.e., Maritime pine sawdust) and isolate lignin. Different parameters, such as LA/FA ratio, temperature, and extraction time, were optimized to boost the yield and purity of extracted lignin. The LA/FA ratio was found to be crucial regarding the superior lignin extraction from the waste biomass. Moreover, the increase in temperature and extraction time enhances the amount of extracted residue but compromises the lignin purity and reduces its molecular weight. The electron microscopy images revealed that biomass samples suffer significant structural and morphological changes, which further suggests the suitability of the new developed bio-fractionation process. Same was concluded by the FTIR analysis, in which no remaining lignin was detected in the cellulose-rich fraction. Overall, the novel combination of bio-sourced FA and LA has shown to be a very promising system for lignin extraction of high purity from biomass waste, thus contributing to extend the opportunities of lignin manipulation and valorisation into novel added-value biomaterials.

Heated tobacco products (HTPs) are newly developed nicotine delivery systems via inhalation of mainstream aerosols generated during the heating of tobacco leaf materials. Previous studies have shown that the amount of chemicals generated is much lower than that generated by conventional combustible cigarettes. However, little attention has been paid to formate, a conjugated base of formic acid with potentially toxic effects on human health. This study aims to understand the actual emission levels of formate in mainstream aerosols produced by commercially available HTP devices in Japan. Aerosols were generated from four types of devices with regular and menthol-type flavours using a vaping machine following the CRM 81 puffing protocol. Formate was tapped in 5 mM sodium carbonate solution and subsequently analysed by ion chromatography. The results showed the total emission amount of formate ranged from 0.0027 ± 0.0031 to 0.27 ± 0.055 mg L-1, varying with heating temperature and flavour type. Moreover, the majority of formate existed as a particulate form due to the weak-basic property of the aerosol, and the formate emission level was much greater than the workplace exposure limit for the direct inhalation of mainstream aerosols. The formate in the mainstream aerosol can be considered a health concern, when using “high-temperature type” HTPs over a long period.