CO2 sequestration: The holy grail of organic chemistry
Let's start by admitting that most humans don't have the discipline or interest to shake their addiction to hydrocarbons. Their populations are mostly greedy people who don't think deeply and who make it politically unpopular to discourage fossil fuels.
Even if you convince a critical mass of countries to lower their CO2 output by reducing consumption, CO2 levels in the air would stay high for a long time and continue to warm the Earth above its equilibrium. CO2 would still need to be removed from the air to stymie global warming.
The reason CO2 is hard to sequester is that it is a low energy compound. Chemical reactions that release CO2 also release energy. There are human made devices that absorb CO2 into new compounds but they require an energy input which is inevitably drawn from burning fossil fuels, thus eliminating any overall reduction of CO2 in the air.
There is however, a way to convert CO2 into hydrocarbon compounds without using fossil fuel energy. It happens every day on a small scale in the leaves of plants and is called photosynthesis. This process harnesses the cellular chemical conditions of a plant (not reproducible in human made devices) and uses sunlight as the external energy source to convert CO2 (low energy) to glucose (high energy). Some of this glucose is eaten by animals or bacteria who convert it back to CO2 and take the energy for themselves. Some of it is polymerized to cellulose to give the plant a strong physical structure. In this form, only bacteria can depolymerize it back to glucose to consume it for energy. When a tree dies its stored cellulose is consumed by bacteria to release CO2 back into the air.
During the carboniferous period (300 million years ago), plants with large cellulosic mass were trapped and subjected to high pressures in a closed system for a long time. This turned their mass of cellulosic carbohydrates (with oxygen) into hydrocarbons (no oxygen and more energy rich). The hydrocarbons are more energy rich due to their high portion of C-H bonds. This is how the fossil fuels were made and it allowed O2 levels in the air to rise enough for animals to appear. These hydrocarbons sat underground withholding CO2 from the air until humans dug them up and to combust in cars, power stations and steel mills.
Humans have also used fossil fuels to make plastics which, as it turns out, are long term stable even when buried. To reverse some of the the CO2 in the air back into a solid state to be safely tucked away, cellulose must be converted into a polymer that is long term stable. Bacteria are known to produce enzymes that animals lack to break cellulose into glucose. The cellulose must be altered by chemical functionalization to prevent bacteria from restoring it to glucose. This will produce a solid, benign polymer that can be buried to remove CO2 from the air.
Then humans can resume burning fossil fuels until they kill each other with more traditional methods.