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Herein, we have specifically designed two metalated porous organic polymers (Zn‐POP and Co‐POP) for syngas (CO+H2) production from gaseous CO2. The variable H2/CO ratio of syngas with the highest efficiency was produced in water medium (without an organic hole scavenger and photosensitizer) by utilizing the basic principle of Lewis acid/base chemistry. Also, we observed the formation of entirely different major products during photocatalytic CO2 reduction and water splitting with the help of the two catalysts, where CO (145.65 μmol g−1 h−1) and H2 (434.7 μmol g−1 h−1) production were preferentially obtained over Co‐POP & Zn‐POP, respectively. The higher electron density/better Lewis basic nature of Co‐POP was investigated further using XPS, XANES, and NH3‐TPD studies, which considerably improve CO2 activation capacity. Moreover, the structure–activity relationship was confirmed via in situ DRIFTS and DFT studies, which demonstrated the formation of COOH* intermediate along with the thermodynamic feasibility of CO2 reduction over Co‐POP while water splitting occurred preferentially over Zn‐POP. [ABSTRACT FROM AUTHOR]

Knowing the environmental spreading pathway of COVID-19 is crucial for improving safety practices, particularly for health care workers who are more susceptible to exposure. This paper focuses on the possible secondary transmission due to resuspension of virus-laden droplets from common surfaces, which several studies have shown to be possible under external disturbances. Such disturbances could be body motion during walking, running, clothes removal, or airflow in the environment. In this paper, a three-dimensional two-phase model is utilized to study respiratory droplet resuspension dynamics on various surfaces due to sudden agitation. The velocity range and variation during walking, surgical glove removal, and dropping an object are studied experimentally. A parametric study is performed to characterize the effects of droplet size and surface wettability on the minimum initial droplet velocity required for detachment from surfaces. The results are reported as average droplet velocity during the detachment process, total detachment time, and detached droplet volume. The obtained results indicate that respiratory droplets larger than 200 μm can detach from typical surfaces due to normal daily activities. Droplets are partially separated from hydrophilic surfaces with contact angle ≤ 90 ° , while the entire droplet is detached from hydrophobic surfaces with contact angle > --> 90 °. Furthermore, the minimum initial droplet velocity to induce the resuspension depends on the droplet size. Droplet velocity immediately after detachment is a function of droplet size, initial droplet velocity, and surface wettability. Bigger droplets have larger detached volume percentage as well as higher velocity after detachment compared to smaller droplets. Finally, a higher initial velocity is needed to separate droplets from hydrophilic surfaces as compared to hydrophobic surfaces. In accordance with the results, the droplet minimum initial velocity to cause detachment is 2 m s−1, while our experiments show that surface velocity can reach up to 3 m s−1 during normal human activities. We also develop an analytical model to predict the required kinetic energy to detach droplets from different surfaces, which is in good agreement with numerical results. The mechanism of droplet detachment is dictated by a competition between droplet kinetic energy induced by surface motion and surface energy due to droplet–surface interaction as well as droplet–vapor and surface–vapor interactions. We believe that the results of this fundamental study can potentially be used to suggest proper surface wettability and safe motion that reduce respiratory droplet resuspension from various surfaces. [ABSTRACT FROM AUTHOR]

Herein, we have designed and synthesized two heteroatom (N, O) rich covalent organic frameworks (COF), PD‐COF and TF‐COF, respectively, to demonstrate their relative effect on CO2 adsorption capacity and also CO2/N2 selectivity. Compared to the non‐fluorinated PD‐COF (BET surface area 805 m2 g−1, total pore volume 0.3647 ccg−1), a decrease in BET surface area and also pore volume have been observed for fluorinated TF‐COF due to the incorporation of fluorine to the porous framework (BET surface area 451 m2 g−1, total pore volume 0.2978 ccg−1). This fact leads to an enormous decrease in the CO2 adsorption capacity and CO2/N2 selectivity of TF‐COF, though it shows stronger affinity towards CO2 with a Qst of 37.76 KJ/mol. The more CO2 adsorption capacity by PD‐COF can be attributed to the large specific surface area with considerable amount of micropore volume compared to the TF‐COF. Further, PD‐COF exhibited CO2/N2 selectivity of 16.8, higher than that of TF‐COF (CO2/N2 selectivity 13.4). [ABSTRACT FROM AUTHOR]

Using a catalyst-free one-pot polycondensation approach, a new donor–acceptor (D–A) based porous polyimide (PeTt–POP) photocatalyst was developed. PeTt–POP produced CH4 (125.63 ppm g−1 in 6 h) from CO2 under visible light irradiation in the gas–solid mode without the use of co-catalysts or sacrificial agents. The progress of the reaction and the corresponding intermediate species involved in the CO2 reduction were identified by operando DRIFTS experiments, from which a plausible reaction mechanism was proposed. [ABSTRACT FROM AUTHOR]