Cessna 172 pilot reported an engine sputter malfunction when switching fuel tanks during cruise. The pilot diverted to an off-line airport and landed safely.

Narrative

I was acting as PIC of a Cessna 172M. The flight mission was a pipeline patrol. I started out at ZZZ1 after topping off at ZZZ1; time XA:16. Then I flew east until reaching ZZZZZ; time XA:56. This was my start point on the pipeline. Then I flew north approx. 1nm and then east approx. 48nm. After the patrol was complete; I continued onto toward ZZZ2 for refueling prior to the next pipeline patrol; time XB:40. I then noticed approx. 4nm northwest of city that the right fuel tank was at 3/4th full while the right tank was only approx. 1/4th full. I attempted to switch the fuel selector to the 'right tank only' location to which the engine started to sputter off around 5-10 seconds later. I quickly switched it back to the both location. I attempted the 'left tank only' to no change in the engine sound and then tried the 'right tank only' a second time to which the engine started to immediately shut-off again. I quickly reselected the 'both tanks' fuel selector location and contacted ZZZ tower of my situation; declaring an urgent fuel situation; time XC:35; location approx. 15nm to the 140° radial from ZZZ. I immediately turned towards ZZZ; time XC:35. I then landed without further incident at XC:49 and taxied to the FBO. I then met up with the firefighting team at the airport who followed me to the FBO and filled out their incident report with Person A. I then met/interviewed with Person B - Deputy Executive Director of Airport Operations ZZZ. Then I called Person C and Person D - Company Management Team informing them of the situation and they agreed to having the FBO Maintenance Department figure out the cause of the incident. Then I called the ZZZ Control Tower and talked to Person E - ATC Manager on staff who was also the ATC Controller who I talked to in the air and on the ground. Person E did not request a safety report but I believe it is worth filling out one anyway. The next day I talked to Person F - FBO Maintenance Manager who stated that the cause of the incident was due to 'Ice blocking right fuel tank supply line from tank.' He stated that potentially fouled fuel from the prior fill-up at ZZZ1 could be to blame but couldn't be certain. FBO cleared the water with a gasculator and returned it for service with all appropriate endorsements as well.