We have, but it's not a single process. We can convert light to electricity quite cheaply and efficiently with solar PV panels and then use that electricity to electrolyze hydrogen from water and capture CO2 from air(or seawater). Then there are a variety of processes, such as the Sabatier reaction, to convert the hydrogen and carbon into a hydrocarbon. I believe Prometheus Fuels is combining the hydrogen electrolysis and CO2 capture into a single step. Terraform Industries is also working on this problem, but is focused on driving down capital costs of electrolysis so that carbon neutral fuel producers can afford to have electrolyzers sitting around unused 75% of the year and only working when solar electricity is so abundant that it's practically free. Electrolysis and carbon capture takes a lot of energy, but assuming that all electricity comes from solar panels, it is far more space efficient than biofuels. An acre of corn or sugarcane can produce about 400-700 gallons of ethanol per year, or about 36-64 gigajoules of fuel. An acre of solar panels (laid nearly flat to maximize space efficiency) that is converted to methane at 30% efficiency (efficiencies around 50-60% are very normal and state of the art is around 75%, but 30% is much easier and cheaper) can produce about 350 gigajoules of fuel per year.

There's also some research on converting hydrogen and CO2 to edible carbohydrates, either chemically or through hydrogenotrophic or methanotrophic bacteria. That will be a huge revolution for either increasing the carrying capacity of the planet or decreasing humanity's impact on the planet. It will also be a huge boon for countries without much arable land to be able to feed their people without relying on imports. Electricity to food is not quite ready for scaling up yet, but synthetic fuels are absolutely ready to go as soon as solar electricity prices drop just a bit more or fossil fuel prices rise a bit more.