The city Ho Chi Minh (HCMC) is one of the largest cities in Vietnam with the most dramatically economic development rate. Along with the economic development, the urbanization process in this city is also taking place very fastly. Due to the rapid urbanization and development, the emission rate from the industry and transportation leads to the increase in the amount of carbon dioxide (CO2) which has been worsening the climate change. Protecting forests and conducting afforestation so that CO2 is transformed to nutrition through photosynthetic conversion is one of the most effective ways to mitigate the effects of climate change. As a result, the accumulation of CO2 emissions has become a global concern. Vegetation absorbs carbon dioxide, helps to conserve the environment, produces oxygen, reduces noise, and helps to stabilize subsurface water. This paper highlights the results of ENVI software which was used to interpret remote sensing images and Arcgis to evaluate the amount of carbon dioxide absorbed by vegetation in each administrative unit: district in HCMC and ward. According to the obtained results, the amount of CO2 absorbed in urban districts “District 1”, “District 3”, “District 4”, “District 5”, “Phu Nhuan District” is immensely low due to the high population density in the center of city. The population is mainly concentrated in the center districts but land area for vegetation is low. Regarding the suburban area, with mangrove forests, Can Gio District has the highest amount of CO2 absorbed of 35,894.075 tons/day and followed by Cu Chi District with 21,548.48 tons/day. It can be indicated that Can Gio and Cu Chi districts improtantly function like the greenhouse gas sinks for the whole HCMC. The success of this study could contribute to climate change mitigation and support in urban and land planning, as well as resettlement policies. Aside from that, CO2 emission and absorption assessment and evaluation in large–scale cities like HCMC has become a crucial, urgent, and practical issue nowadays.

TiO2-based photocatalysts still have some limitations such as large bandgap and low surface area, leading to low efficiency in the photocatalytic degradation of VOCs and limiting it to use in sunlight. Here we report that the nanostructured Ir-doped TiO2 as an efficient photocatalyst generates an excellent risk-reduction material of gaseous toluene. We have succeeded in developing a nanostructured Ir-doped TiO2 and initially found that excellent efficient photocatalytic VOC decomposition can be achieved in our materials The nanostructured Ir-doped TiO2 was synthesized by a one pot, low temperature hydrothermal process with different ratios of Ir doped into the TiO2. It exhibited a high surface area, uniformly spherical morphology of 10–15 nm. Its activity for the photocatalytic degradation of gaseous toluene exhibited up to 97.5% under UV light. This enhancement could be explained by iridium doping which created a high concentration oxygen vacancy and changed the recombination rate of the photogenerated charge carriers. More generally, our study indicates a strategic way to develop the novel nanostructured material for numerous applications.

N–F‐codoped TiO2 materials were successfully fabricated by a hydrothermal method without any capping agent and further heat treatment. The results indicate interstitial N3− ion doping and the surface‐adsorbed F− ion on the TiO2 surface. By introducing N and F into the TiO2 lattice, the band gap of the obtained material is significantly reduced compared to the undoped TiO2. Moreover, the light absorption ability of the material was demonstrated to extend to visible light regions, contributing to the better photocatalytic activity. Furthermore, the sample with the NH4F/TiCl4 precursor molar ratio of 2:1 displayed the greatest photocatalytic activity with visible radiation. This study provides a new pathway to synthesize a novel photocatalyst having great potential for future applications.