I found this[1] article rather interesting, comparing the tVOC and CO2 measured by a consumer device with professional grade equipment. It seems the MOX sensor used in the consumer device (AMS iAQ-CORE-C) did rather well on tVOC, but poorly on CO2 as you mentioned.
The study is interesting but I wouldn't say it "did rather well", as they applied a calibration to it first:
"A regression analysis was performed to improve the accuracy of the Foobot FBT0002100 data relative to the GrayWolf data. Field calibration equations were then produced from the calibration dataset using the results from the GrayWolf instruments as dependent variables and the Foobot FBT0002100 as independent variables and tested on the validation dataset. An analysis in SPSS of the linear, quadratic, and cubic models was performed individually for each parameter to find the most accurate equation."
You can't do that unless you happen to have access to a different research quality sensor. If the Foobot had that out of the factory it'd be nice though.
[1]: https://www.j-sens-sens-syst.net/7/373/2018/ (pdf on the right)