Hey Bob!
So I thought I would elaborate a little bit off of what PharmaMan said, and talk a little bit about biofuels and how that might relate to your project idea.
It turns out that many many scientist now and in the past have been very interested in this idea of using plants as a clean source or energy, because as you pointed out earth has a bit of a problem with how much carbon dioxide is being put into its atmosphere. Plants are a great option for trying to fix the problem because they make energy (sugars) by taking carbon out of the atmosphere. This is different from gas/oil which just releases carbon into the atmosphere.
In fact, plants are so good at this that I would say we don't even need to make artificial chlorophyll, or try to have artificial photosynthesis, because plants and other photosynthetic organisms already do those things really well. If you think about it, photosynthetic life (and evolution) has spent literally billions of years making this awesome system that turns carbon dioxide in our atmosphere into useable energy, so why spend the extra effort trying to come up with a new way to do something when the old way already works so well?
This is the idea behind biofuel. Basically, we can use plants as miniature power plants (hah, no pun intended…) for us. For example, we know that photosynthesis makes sugars, specifically a sugar called glucose, which can basically be thought of as a unit of energy for the plant (or for things that eat plants). However, plants can use glucose like a building block (think legos) to make all sorts of different things. Some of those things are just fancier types of sugar (like the lactose in milk), but some uses of sugar can be for non-energy purposes, such as reinforcement for the plant. That's what cellulose is, it's a whole bunch of sugar that's put together in a way that makes it really tough. It's what makes those strings in celery so hard to chew up, and so they just end up getting stuck in your teeth.
I actually found a project on sciencbuddies (
https://www.sciencebuddies.org/science- ... p038.shtml) that lets you take cellulose from plants and make ethanol. Ethanol is an alcohol; it's actually the type of alcohol that you find in beer, wine, and liquor. Importantly, ethanol actually has a lot of energy in it, and you can run a car on it! So that means you can take a plant, treat it with some chemicals and then run your car using the energy from the sugars in that plant. Maybe a project like this would be something you'd be interested in? Making biofuels actually let's you learn about all sorts of interesting chemistry. This is a project that I would definitely say you would need help with, and hopefully your science teacher could be that help, but I think it would be doable for an 8th grader.
To specifically address your project idea, I would agree with PharmaMan and say that artificially making something that can photosynthesize that wasn't a plant (or some other type of photosynthesizing living thing) would be very very hard. Plants are really complicated, and it takes a lot of work to keep photosynthesis going. It would be tricky to perfectly replicate photosynthesis artificially because there's all sorts of crazy chemistry going on in plants that humans don't know how to do without the help of living things.
I hope this response was helpful and not too long or boring. Please let me know if you want any other information or feedback on your project, and I hope you continue to pursue this idea!
PS Vsauce is amazing! I love that channel so much